Question

The income of a bank on the $n^{th}$ day is Rs $(n^2+2)$ and the expenditure of the bank on the $n^{th}$ day is Rs (2n + 1). Also income $=$ expenditure $+$ savings. In how many days his total savings will be Rs. $1240$?

• A. $10$
• B. $12$
• C. $15$
• D. $16$

Answer 1

The correct option is D $16$

Given:
Income = Expenditure + savings
To calculate: days required for total savings.
Savings = Income - Expenditure.
Savings = Rs.$1240$
Income =Rs. $(n^2+2)$
Expenditure = Rs. $(2n+1)$
From the Equation given:
$n^2+2-(2n+1)=1240$
$(n^2-2n-1239=0$
solving the quadratic equation:
n= $36$ and n=$-34$