Question

find the sum of 21,27,33.....159?​

Answer 1

Answer:

69420

Step-by-step explanation:

Answer 2

Answer:

the answer is 2790

Step-by-step explanation:

A= 21     d = 27 - 21 = 6

An = 159

so,

159 = 21 + (n-1)6

159 + 21 = 6n -6

180 + 6 = 6n

186/6 = n

n = 31

So, Sum =

Sn = n/2 (A + An)

31/2 (21 + 159)

31/2(180)

31 * 90

2790

So, sum of AP is 2790

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