Question

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

Answer 1

Answer:

Step-by-step explanation:

a9=a+(n-1)*d=28

a+8d=28--(1)

sum of 9 terms=(n/2)(2a+(n-1)d)=144

(9/2)(2a+8d)=144

2a+8d=32--(2)

(1) and (2) we get

a=32-28=4

Answer 2

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.