WAEC Past Questions and Answers - Page 1107

5,531.

If events A and B are independent and \(P(A) = \frac{7}{12}\) and \(P(A \cap B) = \frac{1}{4}\), find P(B).

A.

\(\frac{3}{7}\)

B.

\(\frac{4}{7}\)

C.

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

D.

\(\frac{6}{7}\)

Correct answer is A

\(P(A) = \frac{7}{12}\)

\(P(A \cap B) = \frac{1}{4} = P(A) \times P(B)\) (Independent events)

\(\frac{1}{4} ÷ \frac{7}{12} = \frac{1}{4} \times \frac{12}{7} \)

= \(\frac{3}{7}\)

5,532.

If \(\begin{vmatrix} 4 & x \\ 5 & 3 \end{vmatrix} = 32\), find the value of x.

A.

4

B.

2

C.

-2

D.

-4

Correct answer is D

\(\begin{vmatrix} 4 & x \\ 5 & 3 \end{vmatrix} = 12 - 5x = 32\)

\(5x = 12 - 32 = -20\)

\(x = -4\)

5,533.

Profit expressed as a fraction of the selling price is known as

A.

Mark-up

B.

Margin

C.

Gross profit

D.

Net profit

Correct answer is B

No explanation has been provided for this answer.

5,534.

Express \(\frac{1}{1 - \sin 45°}\) in surd form. 

A.

\(2 + \sqrt{2}\)

B.

\(2 + \sqrt{3}\)

C.

\(2 - \sqrt{2}\)

D.

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

Correct answer is A

\(\sin 45 = \frac{\sqrt{2}}{2}\)

\(\frac{1}{1 - \sin 45} = \frac{1}{1 - \frac{\sqrt{2}}{2}}\)

\(\frac{2}{2 - \sqrt{2}} = \frac{4 + 2\sqrt{2}}{4 - 2}\)

= \(2 + \sqrt{2}\)

5,535.

Given that \(f '(x) = 3x^{2} - 6x + 1\) and f(3) = 5, find f(x).

A.

\(f(x) = x^{3} - 3x^{2} + x + 20\)

B.

\(f(x) = x^{3} - 3x^{2} + x + 31\)

C.

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

D.

\(f(x) = x^{3} - 3x^{2} + x - 13\)

Correct answer is C

\(f ' (x) = 3x^{2} - 6x + 1\)

\(f(x) = \int (3x^{2} - 6x + 1) \mathrm {d} x\)

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

\(f(3) = 5 = 3^{3} - 3(3^{2}) + 3 + c\)

\(27 - 27 + 3 + c = 5 \implies 3 + c = 5\)

\(c = 2\)

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