WAEC Mathematics Past Questions & Answers - Page 91

451.

Given that cos x = \(\frac{12}{13}\), evaluate \(\frac{1 - \tan x}{\tan x}\)

A.

\(\frac{5}{13}\)

B.

\(\frac{5}{7}\)

C.

\(\frac{7}{5}\)

D.

\(\frac{13}{5}\)

Correct answer is C

cos x\(\frac{12}{13}\)

132 = 122 + a2

169 = 144 + a2

a2 = 169 - 144

a2 = 25

a \(\sqrt{25}\)

a = 5

tan x = \(\frac{5}{12}\)

\(\frac{1 - \tan x}{\tan x} = \frac{1 - \frac{5}{12}}{\frac{5}{12}}\)

\(\frac{\frac{1 - \frac{5}{12}}{12 - 5}}{12} = \frac{\frac{7}{12}}{\frac{5}{12}}\)

= \(\frac{7}{2} \div \frac{5}{12}\)

= \(\frac{7}{12} \times \frac{12}{5} = \frac{7}{5}\)

452.

If x : y = 3 : 2 and y : z = 5 : 4, find the value of x in the ratio x : y : z

A.

8

B.

10

C.

15

D.

20

Correct answer is C

No explanation has been provided for this answer.

453.

A box contains 13 currency notes, all of which are either N50 or N20 notes. The total value of the currency notes is N530. How many N50 notes are in the box?

A.

4

B.

6

C.

8

D.

9

Correct answer is D

let the number of N50 notes = x let the number of N20 notes = y from the first statement x + y = 13.....(1) from the second statement 50x + 20y = 530 ......(2) dividing through by 10, we have 5x + 2y = 53 ....(20 solving simultaneously by eliminating x + y = 12....(1) 5x + 2y = 53.....(2) multiply eqn (1) by 2 multiply eqn (2) by 1 2x + 2y = 26 -5x + 2y = 53 -3x = -27 x = 9 substitute x = 9 into equation (1) x + y = 13 y = 13 - x = 13 - 9 = 4 y = 4 the number of N50 notes = 9

454.
455.

Which of the following is a measure of dispersion?

A.

range

B.

percentile

C.

median

D.

quartile

Correct answer is A

No explanation has been provided for this answer.