Question

The first term of an ap is -5 and last term is 45. If the sum of the terms is 120, then find the number of terms .

Answer 1

Now, (a1) = -5

(an) = 45

Sum = 120

Sum of AP = (n/2)[(a1)+(an)]

120 = (n/2)(-5+45)

120*2=(n/2)(40)

(240/40)=n

n=6

Number of terms in the AP is 6.

Answer 2

Hope it helps u....!

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