JAMB Mathematics Past Questions & Answers - Page 43

211.

Four boys and ten girls can cut a field first in 5 hours. If the boys work at \(\frac{5}{4}\) the rate at which the girls work, how many boys will be needed to cut the field in 3 hours? 

A.

180

B.

60

C.

25

D.

20

Correct answer is D

Let x rep. numbers of boys that can work at \(\frac{5}{4}\) the rate at

 which the 10 girls work 

For 1 hrs, x boys will work for \(\frac{\frac{1}{5} \times 10}{4}\) 

x = \(\frac{5}{4}\) x 10 

= 8 boys 

8 boys will do the work of ten girls at the same rate 

4 + 8 = 12 bous cut the field in 5 hrs for 3 hrs, 

\(\frac{12 \times 5}{3}\) boys will be needed = 20 boys.

212.

Reach each number to two significant figures and then evaluate \(\frac{0.02174 \times 1.2047}{0.023789}\) 

A.

0

B.

0.9

C.

1.1

D.

1.2

Correct answer is C

\(\frac{0.021741 \times 1.2047}{0.023789}\) = \(\frac{0.0255 \times 1.2}{0.024}\) (to 216) 

= \(\frac{0.0264}{0.024}\) = 1.1

213.

Find all real number x which satisfy the inequality \(\frac{1}{3}\) (x + 1) - 1 > \(\frac{1}{5}\)(x + 4) 

A.

x < 11

B.

x < -1

C.

x > 6

D.

x > 11

Correct answer is D

\(\frac{1}{3}\) (x + 1) - 1 > \(\frac{1}{5}\)(x + 4)  = \(\frac{x + 1}{3} - 1\) > \(\frac{x + 4}{5}\) 

\(\frac{x + 1}{3} - \frac{x + 4}{5} -1\) > 0 

= \(\frac{5x + 5 - 3x - 12}{15}\) 

2x - 7 > 15

2x > 22 = x > 11

214.

Find all median of the numbers 89, 141, 130, 161, 120, 131, 131, 100, 108 and 119 

A.

131

B.

125

C.

123

D.

120

Correct answer is B

Arrange in ascending order

89, 100, 108, 119, 120,130, 131, 131, 141, 161

Median = \(\frac{120 + 130}{2}\) = 125

215.

Evaluate (212)\(_3\) - (121)\(_3\) + (222)\(_3\)

A.

(313)\(_3\)

B.

(1000)\(_3\)

C.

(1020)\(_3\)

D.

(1222)\(_3\)

Correct answer is C

Evaluate (212)\(_3\) - (121)\(_3\) + (222)\(_3\)

(212)\(_3\)  + (222)\(_3\) = 1211\(_3\)

→ 1211\(_3\) - 121\(_3\)

= 1020\(_3\)