Question

A cyber cafe charges ₹20 for the first hour and then ₹10 for subsequent hours. If Ramu plays games for 4 hours, then he has to pay .

• A. ₹40
• B. ₹50
• C. ₹100

Answer 1

The correct option is B ₹50

If we analyse the question carefully, we get to know that the amount Ramu has to pay for each hour forms an arithmetic progression.

The first term, $a$ of the AP is 20, which is the charge for the first hour.
The common difference, $d$ of the AP is 10, which is the amount charged for each additional hour.
i.e., $a=20$ and $d=10$

Since Ramu plays games for 4 hours, he has to pay the amount equivalent of the $4\text{th}$ term of this AP.

Since $n^{\text{th}}$ term of the AP is given by
$a_n=a+(n-1)d,$
we have $a_4=20+(4-1)10.$
$⟹a_4=50$
Hence, Ramu must pay a total of ₹50.