Thread: geometric progression--need help 2

first term is 440 and 12th term is 880. find S6.

so a= 12 r^11 =2 (i think some thing wrong on my calculation )

need help

Originally Posted by nikk

first term is 440 and 12th term is 880. find S6.

so a= 12 r^11 =2 (i think some thing wrong on my calculation )

need help

First term = a = 440.

880 = a r^11 = 440 r^11 => r^11 = 2 => r = ....?

Now substitute a, r and n (= 6) into the sum formula.

it look like my ans up to here still correct

First term = a = 440.

880 = a r^11 = 440 r^11 => r^11 = 2 => r = ....?

so..my last ans is 3108.36

any one can reconfirm it back