JAMB Mathematics Past Questions & Answers - Page 399

1,991.

Calculate the mean deviation of the set of numbers 7, 3, 14, 9, 7, and 8.

A.

13/6

B.

5/2

C.

7/6

D.

7/3

Correct answer is D

x 7 3 14 9 7 8 Total
\(x - \bar{x}\) -1 -5 6 1 -1 0  
\(|x - \bar{x}|\) 1 5 6 1 1 0 14

Mean : \(\frac{7 + 3 + 14 + 9 + 7 + 8}{6} = \frac{48}{6} = 8\)

Mean deviation : \(\frac{\sum |x - \bar{x}|}{n} = \frac{14}{6} = \frac{7}{3}\)

1,992.

The mean of a set of six numbers is 60. If the mean of the first five is 50, find the sixth number in the set.

A.

105

B.

100

C.

95

D.

110

Correct answer is D

Let the sum of the first five numbers and the sixth number be x and t respectively.

\(\frac{x + t}{6} = 60 \implies x + t = 360\)

\(\frac{x}{5} = 50 \implies x = 250\)

\(\therefore t = 360 - 250 = 110\)

1,993.

How many three-digit numbers can be formed from 32564 without repeating any of the digits?

A.

120

B.

10

C.

20

D.

60

Correct answer is D

To get the answer, we simply do

\(\frac{5!}{(5 - 3)!}\)

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

= 60

1,994.
1,995.

The probability of a student passing any exam is 2/3. If the student takes three exams, what is the probability that he will not pass any of them?

A.

2/3

B.

4/9

C.

8/27

D.

1/27

Correct answer is D

P(not passing exam) = \(1 - \frac{2}{3} = \frac{1}{3}\)

P(not passing any of the three exams) = \(\frac{1}{3} \times \frac{1}{3} \times \frac{1}{3}\)

= \(\frac{1}{27}\)