Question

If the sum of the series 24,20,16.....Is 60, then the number of tetms

Answer 1

Here, a = 24, d = 20-24 = -4

Now,

Let there be n terms.

ATP,

n/2 [ 2 x 24 +(n-1)(-4) ] = 60

n/2[48+4-4n]=60

n/2[52-4n]=60

n[26-2n]=60

2n [ 13-n ] = 60

n[13-n]=30

13n-n²=30

n²-13n+30 = 0

(n-3)(n-10)=0

n= 3 or 10

Thus, 3 terms or 10 terms are needed