Question

The minimum number of terms of an A.P. with first term 31 and common difference -2 that must be added to get a negative number?

• A. 31
• B. 32
• C. 33
• D. 34

Answer 1

The correct option is C

33

The sum of n terms of an A.P. = $\frac{n(2a+(n-1\left)d\right)}{2}$
$=\frac{n(62+(n-1\left)\right(-2)}{2}$

Equating it to 0, we get

n = 32

The minimum number of terms required such that adding all terms need to get a negative number is 33.