Question

If a person save 320 in first month , 360 in 2nd month n 400 in third month then in how many month he will save 20000

Answer 1

The given question is of AP.
$a = 320 \: \: d = 40$
an = a+(n-1)d = 20000.
an = 320+(n-1)40 = 20000.
= (n-1)40 = 20000 - 320 = 19680
= (n-1) = 19680/40 = 492
= n = 492+1=493.
The answer is 493.