JAMB Mathematics Past Questions & Answers - Page 276

1,376.

Evaluate \(\frac{3524}{0.05}\) correct to 3 significant figures

A.

705

B.

70,000

C.

70,480

D.

70,500

Correct answer is D

\(\frac{3524}{0.05}\) = 70480

\(\approx\) 70500(3 s.g)

1,377.

Change 7110 to base 8

A.

1078

B.

1068

C.

718

D.

178

Correct answer is A

\(\begin{array}{c|c} 8 & 71 \\ 8 & 8 \text{rem} 7\\ 8 & 1 \text{rem} 0\end{array}\)

= 1078

1,378.

In a survey, it was observed that 20 students read newspapers and 35 read novels. If 40 of the students read either newspapers or novels, what is the probability of the students who read both newspapers and novels?

A.

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

B.

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

C.

\(\frac{3}{8}\)

D.

\(\frac{3}{11}\)

Correct answer is C

40 = 20 - x + x + 35 - x

40 = 55 - x

x = 55 - 40

= 15

∴ P(both) \(\frac{15}{40}\)

= \(\frac{3}{8}\)

1,379.

\(\begin{array}{c|c} x & 1 & 2 & 3 & 4 & 5 \\ \hline f & 2 & 1 & 2 & 1 & 2\end{array}\)
Find the variance of the frequency distribution above

A.

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

B.

\(\frac{9}{4}\)

C.

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

D.

3

Correct answer is B

\(\begin{array}{c|c} x & f & fx & \bar{x} - x & (\bar{x} - x)^2 & f(\bar{x} - x)^2 \\ \hline 1 & 2 & 2 & -2 & 4 & 8\\ 2 & 1 & 2 & -1 & 1 & 1\\ 3 & 2 & 6 & 0 & 0 & 0\\ 4 & 1 & 4 & 1 & 1 & 1\\ 2 & 2 & 10 & 2 & 4 & 8\\ \hline & 8 & 24 & & & 18 \end{array}\)

x = \(\frac{\sum fx}{\sum f}\)

= \(\frac{24}{8}\)

= 3

Variance (62) = \(\frac{\sum f(\bar{x} - x)^2}{\sum f}\)

= \(\frac{18}{8}\)

= \(\frac{9}{4}\)

1,380.

\(\begin{array}{c|c} \text{Class Interval} & 1 - 5 & 6 - 10 & 11 - 15 & 16 - 20 & 21 - 25 \\ \hline Frequency & 6 & 15 & 20 & 7 & 2\end{array}\)
Estimate the median of the frequency distribution above

A.

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

B.

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

C.

12

D.

13

Correct answer is C

Median = L + [\(\frac{\frac{N}{2} - f}{fm}\)]h

N = Sum of frequencies

L = lower class boundary of median class

f = sum of all frequencies below L

fm = frequency of modal class and

h = class width of median class

Median = 11 + [\(\frac{\frac{50}{2} - 21}{20}\)]5

= 11 + (\(\frac{25 - 21}{20}\))5

= 11 + (\(\frac{(4)}{20}\))

11 + 1 = 12