WAEC - Mathematics (1991 - No. 23)
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,
greater than the 1st term by 45, find the 5th term,
3
6
45
48
90
Vysvetlenie
a = 1st term ; ar\(^4\) = 5th term
∴ ar\(^4\) = a(2)\(^4\) = 16a; 16a = 45 + a, a = 3;
3(2)\(^4\) = 48
∴ ar\(^4\) = a(2)\(^4\) = 16a; 16a = 45 + a, a = 3;
3(2)\(^4\) = 48