WAEC Mathematics Past Questions & Answers - Page 172

856.

Simplify\(\frac{3x^{3}}{(3x)^{3}}\)

A.

1

B.

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

C.

\(\frac{1}{9}\)

D.

\(\frac{1}{27}\)

Correct answer is C

\(\frac{3x^{3}}{(3x)^{3}}\\
\frac{3x^{3}}{3x\times 3x\times 3x}=\frac{3\times x\times x\times x}{3\times 3\times 3\times x\times x\times x}=\frac{1}{9}\)

857.

Which of the following is true for the set \(P = \{-3.2\leq x< 5\}\) where x is an integer

A.

least value of x is -3.2

B.

least value of x is -3

C.

greatest value of x is 4.9

D.

greatest value of x is 5

Correct answer is A

No explanation has been provided for this answer.

858.

Simplify \(3\sqrt{45}-12\sqrt{5}+16\sqrt{20}\)leaving your answer in surd form

A.

\(29\sqrt{5}\)

B.

\(14\sqrt{15}\)

C.

\(12\sqrt{15}\)

D.

\(11\sqrt{5}\)

Correct answer is A

\(3\sqrt{45}-12\sqrt{5}+16\sqrt{20}\\
3\sqrt{5\times 9}-12\sqrt{5}+16\sqrt{4\times 5}\\
3\times 3\sqrt{5}-12\sqrt{5}+16\times 2\sqrt{5}\\
9\sqrt{5}-12\sqrt{5}+32\sqrt{5}\\
29\sqrt{5}\)

859.

If \(p\propto \frac{1}{q}\), which of the following is true?

A.

\(\propto p^{2}\)

B.

\(p\propto \frac{1}{q^{2}}\)

C.

\(q\propto \sqrt{p}\)

D.

\(q\propto \frac{1}{p}\)

Correct answer is D

\(p\propto \frac{1}{q} = q \propto \frac{1}{p}\)

860.

Simplify \((0.3\times 10^{5})\div (0.4\times 10^{7})\)leaving your answer in standard form

A.

\(7.5\times 10^{-4}\)

B.

\(7.5\times 10^{-3}\)

C.

\(7.5\times 10^{-2}\)

D.

\(7.5\times 10^{-1}\)

Correct answer is B

\((0.3\times 10^{5})\div (0.4\times 10^{7})\\
\frac{3}{10}\times 10^{5}\div \frac{4}{10}\times 10^{7}=3\times 10^{4}\div 4\times 10^{6}\\
\frac{3\times 10^{4}}{4\times 10^{7}}=\frac{3}{4}\times 10^{-2}=0.75\times 10^{-2}\\
7.5\times 10^{-3}\)