Q15 of 85 Page 110

If a = 2 and d = 4, then S20 = _____

We have a = 2


d= 4


n = 20


we also know that, Sn = × (2a + (n – 1)d)


⇒ S20 = × (2(2) + (20 – 1)4)


⇒ S20 = 10 × (4 + 19 × 4)


⇒ S20 = 10 × (4 + 76)


⇒ S20 = 10 × 80


⇒ S20 = 800


∴ the correct option is (b)

More from this chapter

All 85 →
15

If Sn = 2n2 + 3n, then d =_____

 15

If the sum of the three consecutive terms of A.P. is 48 and the product of the first and the last is 252, then d = _____

 15

If 3 + 5 + 7 + 9 + ... upto n terms = 288, then n = ……

 15

Four numbers are in A.P. and their sum is 72 and the largest of them is twice the smallest. Then the numbers are ………