WAEC Mathematics Past Questions & Answers - Page 156

776.

The table shows the ages(in years) of twenty children chosen at random from a community. What is the median of the distribution? \(\begin{array}{c|c} Age(years) & 1 & 2 & 3 & 4 & 5 \\ \hline {\text {Number of children}} & 2 & 3 & 5 & 6 & 4 \end{array}\)

A.

3.5 years

B.

3.0 years

C.

2.5 years

D.

2.0 years

Correct answer is A

Median = (\(\frac{n + 1}{2})^{th}\)

= \(\frac{20 + 1}{2} = \frac{21}{2}\)

= 10.5

= \(\frac{{\text{10th term and 11th term}}}{2}\)

= \(\frac{3 + 4}{2} = \frac{7}{2}\)

= 3.5yrs

777.

The table shows the ages(in years) of twenty children chosen at random from a community. What is the mean age? \(\begin{array}{c|c} Age(years) & 1 & 2 & 3 & 4 & 5 \\ \hline {\text {Number of children}} & 2 & 3 & 5 & 6 & 4 \end{array}\)

A.

4.46 years

B.

3.35 years

C.

3.30years

D.

3.00 years

Correct answer is B

Mean(age) = \(\frac{(1 \times 2) + (2 \times 3) + (3 \times 5) + (4 \times 6) + (5 \times 4)}{2 + 3 + 5 + 6 + 4}\)

= \(\frac{2 + 6 + 15 + 24 + 20}{20}\)

= \(\frac{67}{20}\)

= 3.35yrs

778.

If the probability of an event occurring is x, what is the probability of the event not occurring?

A.

1 - x

B.

x - 1

C.

0

D.

\(\frac{1}{x}\)

Correct answer is A

If p is the probability of an event happening(occurring) and the probability of an event not occurring is p1 then p + p1 = 1

p1 = 1 - p

x1 = 1 - x