Question 2
The fourth and sixth terms of a Geometric Progression (G.P.) are 54 and 486 respectively.
If r > 0, find the third term.
Observation
The Chief Examiner reported that majority of the candidates that attempted this question did
well.
They were able to express the |
third term as |
𝑎r3 = 54------------- (1) |
and sixth term as |
𝑎𝑟 5 = 486 ----------- (2). |
Dividing equations (2) by (1), 𝑟2= 486⁄ 54 = 9 and this yielded r = 3.
They substituted for in equation (1) and solved for the first term and obtained a = 2.
Then, the third term is 2×32 = 18.