Question

The sum of first 16 terms of the AP : 10,6,2.... is a) - 320 b) 320 c) -352 d) -400 answer step by step plz !!!

Answer 1

$\huge\underline{ \mathbb\red{❥A} \green{n} \mathbb\blue{S} \purple{w} \mathbb \orange{E} \pink{r}} \:</p><p>$

$\mathbf{solution}$

▪️The formula for the sum of first n terms of a AP is n/2(2a+(n-1)d)

▪️here n=16 a=10 d=6-10=2-6=-4

▪️so sum of first 16 terms=16/2(2·10+(16-1)·-4)

▪️=8(20+15·-4)

▪️=8(20-60)

▪️=8(-40)

▪️=-320

▪️therefore the option is A

Answer 2

Answer:

-320 is the answer

Step-by-step explanation:

Sum of 16 terms = n/2(2a+ n-1)d

=16/2(2× 10+16-1)-4

=8×(20+15×-4)

=8×(20+-60)

=8×-40

= -320