Question

Find the sum of first twenty terms of arithmetic series 2+7+12+...using suitable formula

Answer 1

Answer:

a=2

d=5

n=20

So sum = n/2 (2a+(n-1)d)

= 20/2 (2×2 + (20-1)5)

= 10×(4 +95) = 990

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Answer 2

Answer:

990

Step-by-step explanation:

formula: Sn = n/2* (2a+(n-1)d)

where: n=2(the number of terms), a=2(the first term) and d=5(the common difference)

substituting these in the equation;

Sn= 20/2 *(4+(19*5))

calculating this , we get 990

hope this is helpful XD