GEOMETRICAL PROGRESSION 1

The 1st term of a geometric progression is 7 and the 5th term is 567. Find the common ratio.

Solution

G₁=7, G₅=567, n=5

G_n = G₁r^n-1;

G₅ = G₁r^5-1;

G₅ = G₁r⁴;

567 = 7 x r⁴;

567 = 7r⁴;

 7       7

81 = r⁴;  Finding the fourth root of 81,

r = 3

Hence the common ratio is 3.

TRY THIS.........................

The 1st term of a geometric progression is 2 and the 5th term is 162. Find the common ratio.