Test Index

JAMB Mathematics 2015 Paper

© africaexams.com

Question : 12

Total: 61

The first and last term of a linear sequence (AP) are 6 and 10 respectively. If the sum of the sequence is 40. Find the number of terms

nth = 3
nth = 4
nth = 5
nth = 6

Solution:

Concept:

For an arithmetic progression, when the first term

a

and last term

l

are known, the sum is

S_n = \frac{n}{2}(a + l)

.

Explanation:

Given first term

a = 6

, last term

l = 10

, and sum

S_n = 40

.

Substitute into the formula:

40 = \frac{n}{2}(6 + 10)

.

Simplify inside the bracket:

40 = \frac{n}{2} \times 16

.

So

40 = 8n

.

Divide both sides by 8:

n = \frac{40}{8} = 5

.

Answer:

The number of terms is

n = 5

.

© africaexams.com

Go to Question:

Prev Question

Next Question