• # question_answer The first and the last term of an arithmetic progression are 4 and 128, respectively. If the sum of all the terms is 2970, what is the number of terms? A)  40                                B)  45 C)  51                    D)         Cannot be determined

Correct Answer: B

Solution :

We know that, sum of terms of an AP series $\text{=}\,\,\left[ \frac{\text{First}\,\text{term}\,=\text{Last}\,\text{term}}{\text{2}} \right]\,\,\text{ }\!\!\times\!\!\text{ }\,\text{Number}\,\text{of}\,\text{terms}$ $=2950$ $\Rightarrow$   $\left( \frac{4+128}{2} \right)\times \,n=2970$ $\therefore$      $n=45$

You need to login to perform this action.
You will be redirected in 3 sec