GEOMETRIC PROGRESSION 2

The 1st term of a geometric progression is 7 and the 5th term is 112. Find the common ratio.

Solution

G₁=7, G₅=112, n=5

G_n = G₁r^n-1;

G₅ = G₁r^5-1;

G₅ = G₁r⁴;

112 = 7 x r⁴;

112 = 7r⁴;

 7     7

16 = r⁴;  Finding the fourth root of 16,

r = 2

Hence the common ratio is 2.