The sum of first four terms is a G. P. is 30 and that of the last four terms is 960. if its first term is 2 find the common ratio .

If the sum of first four terms in a G.P. is 30 and that of the last four terms is 960, then the sum of the first 8 terms is 990

We also know that a = 2

sum of first 4 terms

= 2(r^4 - 1)(r-1) = 30

r^4 - 1 = 15r - 15

r^4 - 15r + 14 = 0

r = 1 works for the equation , but r = 1 would make all the terms of the

GP the same, so clearly not a solution

r^4 - 15r + 14 = 0 , a bit of trial and error

(r-1)(r - 2)(r^2 + 3r + 7) = 0

so r = 2 or r = not real

check: sum(4) = 2(2^4 - 1)/(2-1) = 30 , as needed

so r = 2 , BUT it does not work for sum(8)

sum(8) = 2(2^8 - 1)(2-1) = 510 , not 990 as necessary according to your second part of the question.

check your question.

72 is the answer to this problem

yes because they have the same amount of green and blur marbles.

step-by-step explanation: