Question

The sum of the first 10 terms of the AP 1, 5, 9….is

• A. 175
• B. 185
• C. 190
• D. 200

Answer 1

The correct option is C 190

The given AP is 1, 5, 9...
first term $a$ = 1, common difference $d$ = 5-1 = 4, no. of terms $n$ = 10 and $S_n$ = sum of all n terms.

Now, $S_n=\frac{n}{2}(2a+(n-1\left)d\right)$

$S_{10}=\frac{10}{2}(2\times 1+(10-1\left)4\right)$

$=5(2+36)=190$