Question

Given that S=n/2(2a+(n-1)d). If a=4,d=3 and n=20 find the value of S​

Answer 1

s=650

Explanation:

s=n/2(2a+(n-1)d)

s=20/2[2x4+(20-1)3]

s=20/2(2x4+19x3)

s=20/2(8+57)

s=20/2x65

s=10x65

s=650

Answer 2

s=650

Explanation:

Sum of 'n' terms formula is given by:-

s=n/2(2a+(n-1)d)

s=20/2[2x4+(20-1)3]

s=20/2(2x4+19x3)

s=20/2(8+57)

s=20/2x65

s=10x65

s=650