Pratik Tibrewal
Last Activity: 11 Years ago
let the A.P. be a, a+d, a+2d, and number of terms be 2n
24 = n/2(2a + (n-1)2d)
=> 24 = n(a+ (n-1)d) ------(1)
30 = n/2(2(a+d) + (n-1)2d)
=> 30 = n(a+d+(n-1)d) ------(2)
also given l - a = 10.5
or a+(2n-1)d - a = 10.5
=> (2n-1)d = 10.5 -----------(3)
from (1): a + (n-1)d = 24/n
put this value in (2)
n(d+24/n) = 30 ----------(4)
substitute the value of d from 3 in 4
n(10.5/(2n-1) + 24/n) = 30
10.5/(2n-1) + 24/n = 30/n
=> 10.5/(2n-1) = 6/n
=> 10.5n = 12n - 6
1.5n = 6
n = 4
Number of terms = 2n = 8
Thanks and Regards,
Pratik Tibrewal
askiitians faculty
BTech
