Question

In a G.P. , the first term is 7, the last term is 448, and the sum is 889. Find the common ratio and the number of terms.

Answer 1

use an=a1*r^(n-1)

Answer 2

where an=48 and a1=7

Answer 3

*448

Answer 4

it is coming r^(n-1)=64

Answer 5

then i used the sum formula Sn=\[Sn =\frac{ a[r^n-1) }{ r-1 }\]

Answer 6

exactly...now you got two equations in two unknowns...so solve for r and n

Answer 7

i am stuck here

Answer 8

where??tell me the second one

Answer 9

\[127=\frac{ r^n-1 }{ r-1 }\]

Answer 10

r comes out to be 2.isn't it??

Answer 11

The answer should come r=2 and n=7

Answer 12

yeah hold on lemme write

Answer 13

ok