WAEC Past Questions and Answers - Page 3918

19,586.

Evaluate \(\frac{x^2 + x - 2}{2x^2 + x -3}\) when x = -1

A.

-2

B.

-1

C.

\(-\frac{1}{2}\)

D.

1

Correct answer is D

\(\frac{x^2 + x - 2}{2x^2 + x - 3}\)

= \(\frac{x^2 + 2x - x - 2}{2x^2 + 3x - 2x - 3}\)

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

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

= \(\frac{x + 2}{2x + 3}\)

At x = -1, 

= \(\frac{-1 + 2}{2(-1) + 3}\)

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

= 1

19,587.

Given that y = px + q and y = 5 when x = 3, while y = 4 when x = 2, find the value of p and q.

A.

p = 1, q = 3

B.

p = 1, q = 2

C.

p = -2, q = 3

D.

p = 3, q = -2

Correct answer is B

y = px + q

5 = 3p + q ... (i)

4 = 2p + q ... (ii)

(i) - (ii) : p = 1

∴∴ 5 = 3(1) + q 

⟹⟹ q = 5 - 3 = 2

(p, q) = (1, 2)

19,588.

A man is four times as old as his son. The difference between their ages is 36 years Find the sum of their ages

A.

45 years

B.

48 years

C.

60 years

D.

74 years

Correct answer is C

Let the sons age be x. The father is 4x ∴ 4x - x = 36; 3x = 36; x = 12 The son is 12 years and the father is 12 x 4 = 48. The sum of their ages (12 + 48) years = 60years

19,589.

Evaluate \(\frac{1}{2}+\frac{3}{4}of\frac{2}{5}\div 1\frac{3}{5}\)

A.

\(\frac{15}{16}\)

B.

\(\frac{11}{16}\)

C.

\(\frac{49}{50}\)

D.

\(3\frac{1}{5}\)

Correct answer is B

\(\frac{1}{2} + (\frac{3}{4} \text{ of } \frac{2}{5}) \div 1\frac{3}{5}\)

= \(\frac{1}{2} + (\frac{3}{4} \times \frac{2}{5}) \div \frac{8}{5}\)

= \(\frac{1}{2} + \frac{3}{10} \div \frac{8}{5}\)

= \(\frac{1}{2} + (\frac{3}{10} \times \frac{5}{8})\)

= \(\frac{1}{2} + \frac{3}{16}\)

= \(\frac{11}{16}\)

19,590.

The nth term of a sequence is \(2^{2n-1}\). Which term of the sequence is \(2^9?\)

A.

3rd

B.

4th

C.

5th

D.

6th

Correct answer is C

\(T_{n} = 2^{2n - 1}\)

\(2^{2n - 1} = 2^9\)

\(2n - 1 = 9 \implies 2n = 9 + 1\)

\(2n = 10 \implies n = 5\)

The 5th term = 2\(^9\)