WAEC Mathematics Past Questions & Answers - Page 79

391.

If \(\frac{\sqrt{2} + \sqrt{3}}{\sqrt{3}}\) is simplified as m + n\(\sqrt{6}\), find the value of (m + n)

A.

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

B.

\(\frac{2}{3}\)

C.

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

D.

1\(\frac{2}{3}\)

Correct answer is C

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

= \(\frac{\sqrt{2} \times \sqrt{3} + \sqrt{3} \times \sqrt{3}}{\sqrt{3} \times \sqrt{3}}\)

= \(\frac{\sqrt{6} + 3}{3}\)

= \(\frac{3 + \sqrt{6}}{3}\)

= Hence, (m + n) = 1 + \(\frac{1}{3}\)


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

392.

Tom will be 25 years old in n years' time. If he is 5 years younger than Bade's present age.

A.

(30 - n)years

B.

(20 - n)years

C.

(25 - n)years

D.

(30 + n)years

Correct answer is A

Let Tom's present agr be x.

Then x = 25 - n

If Tom is 5 years younger than Bade, then Bade's present age is x + 5 = 25 - n + 5

= (30 - n)

393.

In the diagram, VW//YZ, |WX| = 6cm, |XY| = 16cm, |YZ| = 20cm and |ZX| = 12cm. Calculate |VX|

A.

3cm

B.

4cm

C.

6cm

D.

8cm

Correct answer is D

In the diagram, \(\frac{16}{12} = \frac{VX}{6}\) (similar \(\Delta\)s)

VX = \(\frac{16 \times 6}{12}\)

= 8cm

394.

The probability that kebba, Ebou and Omar will hit a target are \(\frac{2}{3}\), \(\frac{3}{4}\) and \(\frac{4}{5}\) respectively. Find the probability that only Kebba will hit the target.

A.

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

B.

\(\frac{7}{60}\)

C.

\(\frac{1}{30}\)

D.

\(\frac{1}{60}\)

Correct answer is C

Hence the probability that only Kebba will hit the target

= P(K)xP(E')xP(O')

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

= \(\frac{1}{30}\)

395.

\(\begin{array}{c|c}
Scores & 0 - 4 & 5 - 9 & 10 - 14\\
\hline Frequency & 2 & 1 & 2\end{array}\)

The table shows the distribution of the scores of some students in a test. Calculate the mean scores.

A.

5.6

B.

6.2

C.

6.6

D.

7.0

Correct answer is D

To calculate the mean of grouped data,

- First step  to determine the midpoint (x) of each interval or class.

0 - 4 ►2

5 - 9  ► 7

 10 - 14  ►12

These midpoints must then be multiplied by the frequencies of the corresponding classes:

2 X 2 = 4 

1 X 7 = 7

2 X 12 = 24

Mean = ( 24 + 7 + 4) ÷ ( 2 + 1 + 2 )

: Mean = 7