1.

In an Arithmetic progression the last term is 28 and the sum of 9 terms is 144 then find the first term.​

Answer»

GIVEN:

Last term of an AP = an = l = 28

Sum of 9 terms of AP = SN = 144

TO FIND:

First term of AP

SOLUTION:

Let the first term be 'a'

We KNOW that,

Sn = n/2 [ a + l]

144 = 9/2 [a + 28]

144 × 2 = 9a + 252

288 = 9a + 252

9a = 288 - 252

9a = 36

=> a = 36/9

=> a = 4

Therefore, the first term (a) = 4.



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