Suppose that $A_i = {1, 2, 3, \ldots, i}$ for $i = 1, 2, 3, \ldots$
Then find $\displaystyle \bigcup_{i=1}^{\infty} A_i = ?$
Here $Z$ denotes the set of integers.
$,\text{Find } \displaystyle \bigcup_{i=1}^{\infty} A_i \text{ and } \bigcap_{i=1}^{\infty} A_i,\ \text{for every positive integer } i \text{ where } A_i={-i,i}.$
(Here $\mathbb Z$ denotes the set of integers.)
Which of the following relations are functions?
(i) ${(1,(a,b)),\ (2,(b,c)),\ (3,(c,a)),\ (4,(a,b))}$
(ii) ${(1,(a,b)),\ (2,(b,a)),\ (3,(c,a)),\ (1,(a,c))}$
(iii) ${(1,(a,b)),\ (2,(a,b)),\ (3,(a,b))}$
(iv) ${(1,(a,b)),\ (2,(b,c)),\ (1,(c,a))}$
A relation $R$ is a function iff every first component occurs exactly once.
(i) first components $1,2,3,4$ appear once each $\Rightarrow$ function.
(ii) $1$ appears twice $\Rightarrow$ not a function.
(iii) $1,2,3$ appear once each $\Rightarrow$ function.
(iv) $1$ appears twice $\Rightarrow$ not a function.
There is a direct flight from Trichy to New Delhi and 2 direct trains.
There are 6 trains from Trichy to Chennai and 4 trains from Chennai to Delhi.
Also, there are 2 trains from Trichy to Mumbai and 8 flights from Mumbai to New Delhi.
In how many ways can a person travel from Trichy to New Delhi?
$Q\to R = T\to F = F$, so $P\to(Q\to R)=T\to F=F$.
$P\to Q = T\to T = T$, $P\to R = T\to F = F$, hence $(P\to Q)\to(P\to R)=T\to F=F$.
Therefore $(F)\to(F)=T$.
Also $Q\vee R = T\vee F = T$, so $P\to(Q\vee R)=T\to T=T$.
The floor function $f(x) = [x]$ maps every real number to the greatest integer less than or equal to $x$.
Different real numbers can have the same floor value, so it is not one-to-one,
but for every integer $n \in \mathbb{Z}$, there exists an $x \in \mathbb{R}$ such that $[x]=n$.
Hence, it is onto but not one-to-one.
For $f(x)$ to be real, both radicals must be defined:
$x - 3 \ge 0 \quad \text{and} \quad x - 4 \ge 0$
$\Rightarrow x \ge 4$
So the domain is $[4, \infty)$.
Let total mathematics students be $M$, chemistry students be $C$, and both be $30$.
\[
0.1M=30 \Rightarrow M=300,\qquad 0.12C=30 \Rightarrow C=250.
\]
At least one $= M+C-\text{both}=300+250-30=520$.
The values of the parameter $a$ such that the roots $\alpha, \beta$ of
$2x^2 + 6x + a = 0$ satisfy the inequality $\dfrac{\alpha}{\beta} + \dfrac{\beta}{\alpha} < 2$ are —
The 120 permutations of “MAHES” are arranged in dictionary order,
as if each were an ordinary 5-letter word.
The last letter of the $86^{th}$ word in the list is —
Total letters = 5 distinct → $5! = 120$ words.
Fixing first letter in alphabetical order: A, E, H, M, S.
Each block = $4! = 24$ words.
After A (24), E (24), H (24) → total = 72.
So the $86^{th}$ word lies in M-block (73–96).
Within M-block, order remaining letters: A, E, H, S.
Each gives $3! = 6$ words.
$73$–$78$: MA… $79$–$84$: ME… $85$–$90$: MH…
Hence, the $86^{th}$ word lies in MH-series.
So the last letter = H.
A person writes letters to 6 friends and addresses the corresponding envelopes.
Let $x$ be the number of ways so that **at least 2 letters** are in wrong envelopes and
$y$ be the number of ways so that **all letters** are in wrong envelopes.
Then find $x - y$.
In how many ways can the following diagram be colored, subject to: (i) Each of the smaller triangles is to be painted with one of three colors — red, blue, or green. (ii) No two adjacent regions have the same color.
The figure has 4 small triangles (1 top, 3 at the base).
Let top be colored in 3 ways.
The 3 base triangles are adjacent, so they must all be different and also different from the top if adjacent.
⇒ Choose color for top: 3 ways
⇒ Choose 3 distinct colors for bottom row (arranged 3! = 6 ways).
⇒ But bottom middle and top are adjacent → exclude same color combinations.
Valid colorings = $3 \times (3! - 3! / 3) = 3 \times 8 = 24.$
From $10!$ onward, every factorial ends with at least two zeros.
So, only the sum of first nine factorials affects the tens digit.
$1! + 2! + 3! + 4! + 5! + 6! + 7! + 8! + 9! = 1 + 2 + 6 + 24 + 120 + 720 + 5040 + 40320 + 362880 = 409113.$
Tens digit = $\boxed{1}.$
Expand $\left(1 + x^2\right)^n = \sum_{k=0}^{n} {}^{n}C_{k}x^{2k}.$
Multiply by $\left(1 + \dfrac{1}{x^2}\right)$:
$= \sum_{k=0}^{n} {}^{n}C_{k}x^{2k} + \sum_{k=0}^{n} {}^{n}C_{k}x^{2k-2}.$
To find middle term → powers of $x$ that are equal when $2k = 2n - (2k-2)$.
Simplifying gives $k = n.$
So middle term = ${}^{2n}C_{n}.$
Let $L = \left(\dfrac{x - 3}{x + 2}\right)^x
= \left(1 - \dfrac{5}{x + 2}\right)^x.$
Take $\ln L = x \ln\!\left(1 - \dfrac{5}{x + 2}\right).$
For large $x$, use $\ln(1 - y) \approx -y$.
So, $\ln L \approx x \left(-\dfrac{5}{x + 2}\right) \to -5.$
Hence, $L = e^{-5}.$
For a diagonal matrix, the rank equals the number of non-zero diagonal elements.
If the rank is $2$, exactly two of $a, b, c$ must be non-zero and one must be zero.
Thus, the possible condition is
$ab \neq 0,\; c = 0$.
Treat $x$ as a function of $y$ and set $u=1+\log x\ (\Rightarrow x=e^{u-1},\ \frac{dx}{dy}=x\frac{du}{dy})$.
The DE becomes
$u\frac{du}{dy}=u-1+e^{\,1+y-u}.$
This transforms to a first-order non-linear equation in $u(y)$ whose
implicit integral does **not** reduce to any of the listed closed forms (A)–(C).
With the initial condition $y(1)=0$ (i.e., $u=1$ at $y=0$), the solution is an
implicit relation not matching (A)–(C).
Every gram of wheat provides $0.1$ gram of proteins and $0.25$ gram of carbohydrates.
The corresponding values of rice are $0.05$ gram and $0.5$ gram respectively.
The minimum daily requirements of proteins and carbohydrates for an average child are $50$ gram and $200$ gram respectively.
Then in what quantities wheat and rice be mixed in daily diet to provide minimum daily requirement of proteins and carbohydrates at minimum cost?
Solution:
Corner points by solving the constraints:
$(0,5),\ (3,0),\ \left(\frac{1}{2},\frac{5}{2}\right)$
Now compute $Z = 7x + y$:
At $(0,5): Z = 5$
At $(3,0): Z = 21$
At $\left(\frac{1}{2},\frac{5}{2}\right): Z = \frac{7}{2} + \frac{5}{2} = 6$
Minimum $Z = 5$ at $(0,5)$
Solution:
For $x \in [n,n+1)$, we have $[x]=n$.
$\displaystyle \int_n^{n+1} e^{\,x-[x]}dx
= e^{-n}\!\int_n^{n+1} e^{x}dx
= e^{-n}(e^{n+1}-e^{n})=e-1.$
The interval $[0,1000)$ has $1000$ such unit pieces, so the total integral is
$1000(e-1)$.
Solution:
Let $t=x^3 \Rightarrow dt=3x^2dx$, so
$y=\dfrac{1}{3}e^{x^3}+C$.
Using $(0,1)$: $1=\dfrac{1}{3}+C \Rightarrow C=\dfrac{2}{3}$.
Hence $3y-2=e^{x^3} \Rightarrow x^3=\log_e(3y-2)$, so
$x=\sqrt[3]{\log_e(3y-2)}$.
Solution:
$\sin^{4}x\cos^{4}x=\big(\sin^{2}x\cos^{2}x\big)^2
=\left(\dfrac{\sin 2x}{2}\right)^{4}
=\dfrac{1}{16}\sin^{4}2x.$
Thus
$J=\displaystyle\int_{0}^{\pi/2}\sin^{4}x\cos^{4}x\,dx
=\dfrac{1}{16}\!\int_{0}^{\pi/2}\!\sin^{4}2x\,dx
=\dfrac{1}{32}\!\int_{0}^{\pi}\!\sin^{4}u\,du.$
Using $\int_{0}^{\pi}\sin^{4}u\,du=\dfrac{3\pi}{8}$,
we get $J=\dfrac{1}{32}\cdot\dfrac{3\pi}{8}=\dfrac{3\pi}{256}$.
Solution:
Work modulo $64$.
$49\equiv -15\pmod{64}$ and
$49^{1}\equiv49,\ 49^{2}\equiv33,\ 49^{3}\equiv17,\ 49^{4}\equiv1$;
hence $49^{n}$ is periodic with period $4$.
Also $16n\equiv 0,16,32,48\ (\bmod\ 64)$ for $n\equiv 0,1,2,3$.
For each residue class:
$n\equiv0$: $1+0+\lambda\equiv0\Rightarrow \lambda\equiv -1$
$n\equiv1$: $49+16+\lambda\equiv1+\lambda\equiv0$
$n\equiv2$: $33+32+\lambda\equiv1+\lambda\equiv0$
$n\equiv3$: $17+48+\lambda\equiv1+\lambda\equiv0$
All give $\lambda\equiv -1\pmod{64}$.
The least negative representative is $\boxed{-1}$.
Solution:
A Disk Defragmenter is a **system utility** that rearranges fragmented data on a disk
so that files are stored in contiguous sectors, improving access speed and efficiency.
Hence, it belongs to the category of **Utility Programs**.
Solution:
**ISCII (Indian Standard Code for Information Interchange)** is the encoding scheme
developed specifically for representing Indian scripts such as Devanagari, Tamil, Bengali, etc.
Consider the following C language declarations & statements.
Which statement is erroneous?
float f1 = 9.9;
float f2 = 66;
const float *ptrF1;
float * const ptrF2 = &f2;
ptrF1 = &f1;
ptrF2++;
ptrF1++;
- `const float *ptrF1;` → pointer to constant float, can move pointer, not modify value.
- `float * const ptrF2 = &f2;` → constant pointer to float, cannot change address, but can modify value.
- Statement `ptrF2++` tries to move a **constant pointer**, which is **not allowed**.
Hence, `ptrF2++` is **erroneous**.
Solution:
Operator `^` is **bitwise XOR**.
$n1 = 3 \Rightarrow 011_2$
$n2 = 6 \Rightarrow 110_2$
$n1 \oplus n2 = 101_2 = 5$
Variable `a` is declared but **not initialized**.
Using an uninitialized variable in expression `(a ^ a)` causes **undefined behavior**.
Hence, the program compiles but produces a **run-time error or unpredictable result**.
Solution:
In C, the range of `char` is from $-128$ to $127$.
When we assign $130$ to a `char`, it overflows:
$130 - 256 = -126$
Thus the value stored in `ch` is $-126$.
Output:
value of ch = -126
Solution:
`%i` reads an integer and **skips leading whitespace**, so it consumes `29`.
`%c` reads the **next character exactly as-is** (does **not** skip whitespace).
The next character after `29` is the space.
Therefore: $i=29$, $c=$ space `' '`.
Solution:
When a local variable has the same name as a global variable,
the **local variable overrides** (takes precedence over) the global one inside its block.
Thus (C) is **invalid** for C.
C was originally developed in the 1970s by Dennis Ritchie at Bell Telephone Laboratories, Inc.,
which is an outgrowth of two earlier languages, called:
Solution:
VoIP = Voice over Internet Protocol — used for calling over the internet.
All three — WhatsApp, FaceTime, and IMO — support VoIP.
So none of these options is correct.
Solution:
Statement (B) is **incorrect** — tightly coupled systems are **not** necessarily more energy-efficient than clusters; clusters can be optimized for energy efficiency.
Android devices natively support **FAT32** and **exFAT** file systems.
However, **NTFS** is not fully supported without third-party drivers or root access.
Masked ROM, EEPROM, and Flash BIOS are all types of **Read Only Memory (ROM)**.
- **Flash drive** is a type of **secondary storage (non-volatile)** device, not ROM.
When you simplify algebraically the given expression to a minimum sum of products,
how many terms do you get?
(A + B' + C + E') (A + B' + D' + E) (B' + C' + D' + E')
Solution:
Let’s analyze:
We can simplify using Boolean algebra rules.
After simplification (by K-map or expansion reduction), the minimum sum of products results in **4 terms**.
Solution:
Simplify step-by-step:
$A'CD'E + A'B'D' + ABCE + ABD$
→ Combine using absorption and distributive laws.
$A'B'D' + ABD + ACD'E$
Hence, the final simplified expression is:
Solution:
5th Generation Languages (5GL) are logic-based, AI-oriented languages that use **constraints** and **declarative problem-solving**, not step-by-step coding.
Examples: Prolog, Mercury, OPS5, etc.
- ASP and JavaScript → 4th generation or scripting languages
- SQL → 4th generation language
Hence, none of these belong to 5GL.
Solution:
String: "\nhello"
Character positions:
0:'\n' 1:'h' 2:'e' 3:'l' 4:'l' 5:'o'
→ "\nhello" + 3 points to index 3, i.e., `"llo"`
Hence it prints “llo”.
```ruby
Solution:
The function `count()` counts number of 1-bits in the binary representation of `x`.
For `a = 3`
Binary of 3 = `11`
→ Number of 1 bits = 2
Hence output = 2.
Solution:
In the **ternary operator** `(expr₁ ? expr₂ : expr₃)`,
the **data type of result** is the **common type** of `expr₂` and `expr₃`.
Here,
- `expr₁` → condition (float type, irrelevant for result type)
- `expr₂` → int
- `expr₃` → (not specified but implied same as expr₂ type logic)
When int and float are combined → **result type = float** (implicit type conversion).
Solution:
Operator precedence (from high to low in C):
`[]` > `<` > `?:` > `,`
Therefore, the highest precedence among these is **array subscript `[ ]`**.
Operator associativity in C:
- Most unary operators (!, ++, --, sizeof, etc.) → **Right to Left**
- Conditional (`?:`) → **Right to Left**
- Comma operator (`,`) → **Left to Right**
Hence, only the **comma operator** has **left-to-right** associativity.
Solution:
In C, **“else” is always paired with the nearest unmatched “if”** (no braces rule).
Here:
- The inner `if (array[i] > 0)` is the **nearest unmatched `if`** before `else`.
So, the `else` is paired with the **second (inner)** `if`.
Solution:
The **argc (argument count)** includes the program name itself.
So the arguments are:
1️⃣ "copy" (program name)
2️⃣ "file1"
3️⃣ "file2"
4️⃣ "file3"
Thus, total arguments = 4.
Solution:
- `"r+b"` or `"rb+"` → open **existing file** for both reading and writing (no truncation).
- `"w+b"` or `"wb+"` → open file for reading and writing but **creates/truncates** file.
- `"ab"` → append binary mode.
Hence, the correct mode for **existing file in read-write** is `"r+b"`.
Solution:
- `p--` → post-decrement (use then decrement)
- `--p` → pre-decrement (decrement then use)
Here, we need to **decrement p first**, then fetch the value it points to.
Hence, correct expression: `*--p`
How many times this statement will execute:
for (; *s == *t && *t != '\0'; s++, t++)
if both character pointers ‘s’ and ‘t’ point to the same string “abc”.
Solution:
C99 added these new keywords:
- `_Bool`
- `inline`
- `restrict`
- `_Complex`
- `_Imaginary`
`register` is an **old ANSI C keyword**, not added in C99.
Solution:
Valid C versions are:
- C89 (ANSI standard, 1989)
- C90 (ISO standard, 1990)
- C99, C11, C17, and C23
There is **no version called C2007 or CIX**.
Solution:
“Patronage” means **support, sponsorship, or backing**, especially in the sense of helping an individual, organization, or activity.
Hence, synonym is **support**.
Solution:
Sentence is in **past tense** (“Did you think”),
so the action that happened **before** that must be in **past perfect tense**.
Correct form: “Did you think you **had seen** me somewhere before?”
Choose the correct preposition:
He was of a charitable disposition, but did not like a number of his relatives trying to live …………….. him without trying to earn their living.
Solution:
Active voice: “A stone struck me on the head.”
→ Subject: A stone
→ Object: me
→ Verb: struck
Passive structure: **Object + was/were + past participle + by + Subject**
✅ Correct passive: “I was struck on the head by a stone.”
Solution:
Work column-wise with a constant step of −8 in alphabet positions (A=1,…,Z=26):
Col1: Z(26) → R(18) → ? ⇒ 26−8=18−8=10 ⇒ J
Col2: ? → O(15) → G(7) ⇒ top must be 23 ⇒ W
Col3: S(19) → ? → C(3) ⇒ middle must be 11 ⇒ K
Thus the three letters (top-middle, middle-right, bottom-left) are W, K, J → “WKJ”.
In a row of men, Manoj is 30th from the right and Kiran is 20th from the left.
After interchanging their positions, Manoj becomes 35th from the right.
What is the total number of men in the row?
Solution:
Day shifts year-to-year by +1 for a common year, +2 for a leap year.
1965→66: +1 (Wed)
1966→67: +1 (Thu)
1967→68: +1 (Fri)
1968 is leap ⇒ 1968→69: +2 (Sun)
1969→70: +1 (Mon)
1970→71: +1 (Tue)
So next Tuesday falls on **5 Jan 1971**.
Sunil is the son of Kesav. Simran (Kesav’s sister) has a son Maruti and daughter Sita.
Prem is the maternal uncle of Maruti. How is Sunil related to Maruti?
Solution:
Look at odd and even positions separately.
Odd positions (1,3,5,7,9,11,13): b, a, ?, b, ?, b, ? → pattern = "bab" repeating ⇒ 5=b, 9=a, 13=b.
Even positions (2,4,6,8,10,12,14): a, b, a, a, b, a, ? → pattern = "aba" repeating ⇒ 14=a.
Missing terms (in order 5th, 9th, 13th, 14th) = b, a, b, a → **baba**.
Solution:
Two interleaved sequences:
- 1st,3rd,5th,7th,…: Z(26), X(24), V(22), T(20) ⇒ decreasing by 2 ⇒ next = R(18).
- 2nd,4th,6th,8th,…: L(12), J(10), H(8), F(6) ⇒ decreasing by 2 ⇒ next = D(4).
So the next two letters are **R, D**.
""
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