WAEC Mathematics Past Questions & Answers - Page 228

1,136.

What fraction must be subtracted from the sum of \(2\frac{1}{6}\) and \(2\frac{7}{12}\) to give \(3\frac{1}{4}\)?

A.

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

B.

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

C.

\(1\frac{1}{6}\)

D.

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

Correct answer is D

\(2\frac{1}{6} + 2\frac{7}{12}\)

= \(\frac{13}{6} + \frac{31}{12}\)

= \(\frac{26 + 31}{12}\)

= \(\frac{57}{12} = \frac{19}{4}\)

\(\frac{19}{4} - 3\frac{1}{4}\)

= \(\frac{19}{4} - \frac{13}{4}\)

= \(\frac{6}{4}\)

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

1,137.

Find the missing number in the addition of the following numbers, in base seven
\(\begin{matrix}
4 & 3 & 2 & 1\\
1 & 2 & 3 & 4\\
* & * & * & *\\
1&2&3&4&1
\end{matrix}\)

A.

3453

B.

5556

C.

6016

D.

13453

Correct answer is A

4321\(_7\) + 1234\(_7\) = 5555\(_7\)

Missing number = 12341\(_7\) - 5555\(_7\)

= 3453\(_7\)

1,138.

Simplify \(\frac{10}{\sqrt{32}}\)

A.

\(\frac{5}{4}\sqrt{2}\)

B.

\(\frac{4}{5}\sqrt{2}\)

C.

\(\frac{5}{16}\sqrt{2}\)

D.

\(\frac{16}{5}\sqrt{2}\)

Correct answer is A

\(\frac{10}{\sqrt{32}}=\frac{10}{\sqrt{16\times 2}} = \frac{10}{4\sqrt{2}}\\
\frac{10\times \sqrt{2}}{4\sqrt{2}\times\sqrt{2}}=\frac{10\sqrt{2}}{4\times 2}= \frac{5}{4}\sqrt{2}\)

1,139.

Express 398753 correct to three significant figures

A.

398000

B.

398700

C.

398800

D.

399000

Correct answer is D

398753 \(\approxeq\) 399000 (to 3 s.f)

1,140.

Express \(\frac{7}{19}\) as a percentage, correct to one decimal place

A.

2.7%

B.

3.7%

C.

27.1%

D.

36.8%

Correct answer is D

\(\frac{7}{19}\) as a percentage will be
\(\frac{7}{19}\times \frac{100}{1}\% = 36.8\%\)