Question

The sum of some terms of GP. is 3 1 5 whose first term and the common ratio are 5 and 2, respectively. Find the last term and the number of terms.

Answer 1

hope this will help u... :-)

Answer 2

Answer:

the number of terms = 6

Last term  = 160

Step-by-step explanation:

First Term = a = 5

Common ratio = r = 2

let say number of terms = n

Sum of n Terms = a(rⁿ - 1)/(r - 1)

= 5 (2ⁿ - 1)/(2 - 1)

= 5 (2ⁿ - 1)

5 (2ⁿ - 1) = 315

=> 2ⁿ - 1 = 63

=> 2ⁿ = 64

=> n = 6

the number of terms = 6

Last term = arⁿ⁻¹  = ar⁵  = 5 * 2⁵ = 160

Last term  = 160