Investment Doubling Problem

A man invests Rs. 5,000 in each of the years 1990, 1995, 2000, and 2005.
His investment doubles every 5 years.
Find the total amount he receives in 2010.

Doubling period = 5 years

For each investment, amount in 2010 is calculated as:
$$ A = P \times 2^{\frac{t}{5}} $$ where
\( P = \) principal (Rs. 5,000),
\( t = \) years invested (difference between 2010 and investment year).

• Investment in 1990 (20 years):
  $$ A = 5000 \times 2^{\frac{20}{5}} = 5000 \times 2^{4} = 5000 \times 16 = 80000 $$
• Investment in 1995 (15 years):
  $$ A = 5000 \times 2^{\frac{15}{5}} = 5000 \times 2^{3} = 5000 \times 8 = 40000 $$
• Investment in 2000 (10 years):
  $$ A = 5000 \times 2^{\frac{10}{5}} = 5000 \times 2^{2} = 5000 \times 4 = 20000 $$
• Investment in 2005 (5 years):
  $$ A = 5000 \times 2^{\frac{5}{5}} = 5000 \times 2^{1} = 5000 \times 2 = 10000 $$

Total Amount in 2010 = \( 80000 + 40000 + 20000 + 10000 = \boxed{150000} \) Rs.