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The common ratio of a G.P is 2. If the 5th term is greater than the 1st term by 45, find the 5th term

+1 vote
asked Mar 1, 2013 in BASIC MATH by Afeez Novice

1 Answer

+2 votes
 
Best answer

If the first term of a GP is ‘a’ and the common ratio is r, then the n’th term is: ar^(n − 1).

5th term is greater than 1st term by 45. ar^4 - a = 45.

Substitute r = 2 in the expression.

a*2^4 - a = 45

16a - a = 45

15 a = 45

a = 3

5th term = ar^(5 -1) = 3 * 2^4 = 48

answered Mar 1, 2013 by John Lyn Pupil
selected Mar 1, 2013 by Afeez

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