Question

which term of the given series would be the first one to be a four digit number:192 288 432 648.....?

Answer 1

Given Series is 192, 288, 432, 648.

Now,

First-term a1 = 192.

Common ratio r = 288/192

                           = 3/2.



We know that an = a1. r^(n - 1).

= > an = 192. (3/2)^(n - 1)

Now,

5th term = 192(3/2)^(5 - 1)

               = 192(3/2)^4

               = 192(81/16)

               = 972.



6th term = 192(3/2)^(6 - 1)

               = 192(3/2)^5

               = 192(243/32)

               = 1458.



The series is 192,288,432,648,972,1458....


Therefore 6th term will be the first one to be a four-digit number. 



Hope this helps!