2000 - WAEC Mathematics Past Questions & Answers - page 1

1
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 OPTION: d
\(\frac{7}{19}\) as a percentage will be
\(\frac{7}{19}\times \frac{100}{1}\% = 36.8\%\)
2

Express 398753 correct to three significant figures

A
398000
B
398700
C
398800
D
399000
CORRECT OPTION: d

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

3
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 OPTION: a
\(\frac{10}{\sqrt{32}}=\frac{10}{\sqrt{16\times 2}} = \frac{10}{4\sqrt{2}}\
\frac{10\times \sqrt{2}}{4\sqrt{2}\times\sqrt{2}}=\frac{10\sqrt{2}}{4\times 2}= \frac{5}{4}\sqrt{2}\)
4

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 OPTION: a

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

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

= 3453\(_7\)

5

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 OPTION: d

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

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

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

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

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

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

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

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

6
Simplify \(\left(\frac{16}{81}\right)^{-\frac{3}{4}}\times \sqrt{\frac{100}{81}}\)
A
\(\frac{80}{243}\)
B
\(\frac{1}{64}\)
C
\(\frac{25}{6}\)
D
\(\frac{15}{4}\)
CORRECT OPTION: d
\(\left(\frac{16}{81}\right)^{-\frac{3}{4}}\times \sqrt{\frac{100}{81}}\
\frac{1}{\left(\sqrt[4]{\frac{16}{81}}\right)^3}\times \frac{10}{9}=\frac{1}{\left(\frac{2}{3}\right)^3}\times\frac{10}{9}\
=\frac{27}{8}\times \frac{10}{9}=\frac{15}{4}\)
7
Which of the following numbers is perfect cube?
A
350
B
504
C
950
D
1728
CORRECT OPTION: d
8

If \(104_x = 68\), find the value of x

A
5
B
7
C
8
D
9
CORRECT OPTION: c

\(104_x = 68\
1 \times x^2 + 0 \times x + 4 \times x^0 = 68\
x^2 = 68 - 4; x^2 = 64\
x = \sqrt{64}=8\)

9

The ages of three men are in the ratio 3:4:5. If the difference between the ages of the oldest and youngest is 18 years, find the sum of the ages of the three men

A
45 years
B
72 years
C
108 years
D
216 years
CORRECT OPTION: c

Given that the ages are in the ratio 3: 4: 5.

Let the sum of their ages be t.

\(\therefore\) The youngest age = \(\frac{3}{12} t\)

The eldest age = \(\frac{5}{12} t\)

\(\implies \frac{5}{12} t - \frac{3}{12} t = 18\)

\(\frac{2t}{12} = 18 \implies t = \frac{18 \times 12}{2}\)

t = 108 years.

The sum of their ages = 108 years.

10

Given that \(log_4 x = -3\), find x.

A
\(\frac{1}{81}\)
B
\(\frac{1}{64}\)
C
64
D
81
CORRECT OPTION: b

\(\log_4 x = -3\)

\(x = 4^{-3}\)

= \(\frac{1}{64}\)

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