Question

George earned Rs. $12$ in the first day, Rs. $18$ in the second day and Rs. $24$ in the third day and so on. How much did he earn in the first $6$ days?

• A. $160$
• B. $161$
• C. $162$
• D. $163$

Answer 1

Answer: (C)

$162$

The sequence is $12,18,\mathrm{24......}$
$a=12,d=6$
First find the common difference:
$a_n=a_1+(n-1)d$
$a_6=12+(6-1)6$
$=12+5\times 6$
$a_6=42$
We know that, $S_n=\frac{n}{2}$ [First term $+$ Last term]
$=\frac{6}{2}[12+42]$
$=3\left[54\right]$
$S_6=162$
So, George earned Rs. $162$ in $6$ days.