In an AP : given l = 28, s n = 144 and there are 9 terms Find and a

Question

Philoid · Accepted Answer

Given

Last term (l) = 28

Sum of the series s_n = 144

The number of terms in the series (n) = 9

We have another formula to find sum of the series, when common difference is not given

Sum of the series s_n = [a +l]

Where a is the first term

144 = [a + 28]

32 = a + 28

4 = a

∴ first term (a) = 4.

In an AP :given l = 28, sn = 144 and there are 9 terms Find and a