A man's investment doubles in every 5 years. If he invested ₹ 5000 in each of the years 1990, 1995, 2000 and 2005, then what was the total amount received by him in 2010?
(a)₹ 30000
(b)₹ 70000
(c)₹ 140000
(d)₹ 150000
Answer
Answer (as printed): D
Explanation
Total amount received by the man in 2010 $$\begin{aligned} & =₹\left[\left(5000 \times 2^{4}\right)+\left(5000 \times 2^{3}\right)+\left(5000 \times 2^{2}\right)+(5000 \times 2)\right] \\ & =₹(80000+40000+20000+10000)=₹ 150000 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.