Question

Find the ${20}^{th}$ term from the last term of the AP: 3, 8, 13, ...., 253.

• A. 152
• B. 164
• C. 158
• D. 182

Answer 1

The correct option is C

158

We want to find ${20}^{th}$ term from the last term of given AP. So, let’s write given AP in this way: 253... 13, 8, 3

First term = $a=253$

Common Difference = $d=8-13=-5$

Using formula $a_n=a+(n-1)d$, to find $n^{th}$ term of arithmetic progression, we can say that

$a_{20}=253+(20-1)(-5)$

$\Rightarrow$ $a_{20}=253+19(-5)=253-95=158$

Therefore, the ${20}^{th}$ term from the last term of given AP is 158.