Question

A man saves ` 135 in the first year, ` 150 in the second year and in this way he increases his savings by ` 15 every, year. In what time will his total saving be ` 5550?

• A. 20 yr
• B. 25 yr
• C. 30 yr
• D. 35 yr

Answer 1

Answer: (A)

Let the required time be n years. $\therefore$ $5550=135+150+...+n$ terms $=\frac{n}{2}[2\times 135+(n-1)15]$ $\Rightarrow$ $2\times 5550=270n+n(n-1)15$ $\Rightarrow$ $740=18n+n^2-n$ $\Rightarrow$ $n^2+17n-740=0$ $\Rightarrow$ $(n-20)(n+37)=0$ $\Rightarrow$ $n=20yr$ ( $\because$ $n$ cannot be negative)