WAEC Mathematics Past Questions & Answers - Page 122

606.

If a number is chosen at random from the set {x: 4 \(\leq x \leq 15\)}. Find the probability that it is a multiple of 3 or a multiple of 4

A.

\(\frac{1}{12}\)

B.

\(\frac{5}{12}\)

C.

\(\frac{7}{12}\)

D.

\(\frac{11}{12}\)

Correct answer is C

set = 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

multiple of 3 = 6, 9, 12, 15

multiple of 4 = 4, 8, 12

Prob(multiple of 3 or 4) = Prob(multiple of 3) + pro(multiple of 4)

= \(\frac{4}{12} + \frac{3}{12} = \frac{7}{12}\)

607.

Solve the equation; 3x - 2y = 7, x + 2y = -3

A.

x = 1, y = -2

B.

x = 1, y = 3

C.

x = -2, y = -1

D.

x = 4, y = -3

Correct answer is A

3x - 2y = 7; Solve by elimination method

x + 2y = -3

3x - 2y = 7.....(i)

-3x + 6y = -9.....(ii)

-8y = 16

y = \(\frac{16}{-8} = -2\)

Put y = -2 into equation (i); 3x - 2y = 7

3x - 2(-2) = 7

3x + 4 = 7

3x = 7 - 4

3x = 3

x = \(\frac{3}{3}\) = 1

608.

Given that cos xo = \(\frac{1}{r}\), express tan x in terms of r

A.

\(\frac{1}{\sqrt{r}}\)

B.

\(\sqrt{r}\)

C.

\(\sqrt{r^2 + 1}\)

D.

\(\sqrt{r^2 - 1}\)

Correct answer is D

cos xo = \(\frac{1}{r}\); \(\sqrt{r^2 - 1}\)

By Pythagoras r2 = 12 + x2 - 1

x = \(\sqrt{r^2 - 1}\)

tan xo = \(\sqrt{r^2 - 1}\)

= \(\sqrt{r^2 - 1}\)

609.

Solve for x in the equation; \(\frac{3}{5}\)(2x - 1) = \(\frac{1}{4}\)(5x - 3)

A.

zero

B.

1

C.

2

D.

3

Correct answer is D

\(\frac{3}{5}\)(2x - 1) = \(\frac{1}{4}\)(5x - 3)

\(\frac{6x}{5} - \frac{3}{5} = \frac{5x}{4} - \frac{3}{4}\)

\(\frac{6x}{5} - \frac{5x}{4} = \frac{3}{5} - \frac{3}{4}\)

\(\frac{24x - 25x}{20} = \frac{12 - 15}{20}\)

\(\frac{-x}{20} = \frac{-3}{20}\)

-20x = -60

x = \(\frac{-60}{-20}\)

x = 3

610.

If N112.00 exchanges for D14.95, calculate the value of D1.00 in naira

A.

0.13

B.

7.49

C.

8.00

D.

13.00

Correct answer is B

D14.95 = N112.00

D1.00 = \(\frac{N112}{D14.95} \times\) D1.00

= 7.49