Question

if sum of n terms of AP 2, 5, 8 and so on so is 155 then the number of terms is ​

Answer 1

Answer:

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Sn= n÷2(2a+(n-1)d)

155=n÷2(2×2+(n-1)3)

155=n÷2(3n+1)

310=3n^2+n

3n^2+n-310

by solving we get

n=10

then last term =

a+ (n-1)d= 2+(10-1)3=

2+27=29

Answer 2

Step-by-step explanation:

155 =2+(n-1) 3

155 =2+3n-3

154 = 3n

154/3 = n