JAMB Mathematics Past Questions & Answers - Page 339

1,691.

Solve for x in 8x-2 = 2/25

A.

4

B.

5

C.

8

D.

10

Correct answer is D

8x-2 = 2/25

x-2 = 2/25 x 1/8

x-2 = 2/200

x-2 = 1/100

1/x2 = 1/100

x2 = 100

x = 10

1,692.

If log7.5 = 0.8751, evaluate 2 log75 + log750

A.

6.6252

B.

6.6253

C.

66.252

D.

66.253

Correct answer is B

If log 7.5 = 0.8751
Then 2log75 + log750
= 2(1.8751) + 2.8751
= 3.7502 + 2.8751
= 6.6253

1,693.

A man donates 10% of his monthly net earnings to his church. If it amounts to N4,500, what is his net monthly income?

A.

N40,500

B.

N45,000

C.

N52,500

D.

N62,000

Correct answer is B

Let;
M = Man monthly net earnings

Then;

\(\text{N4500} = \frac{\text{10%}}{\text{100%}} \times M \)

\(M = \frac{\text{N4500} \times \text{100%}}{\text{10%}} \)

M = N45,000

1,694.

Express the product of 0.00043 and 2000 in standard form.

A.

8.6 x 10-3

B.

8.3 x 10-2

C.

8.6 x 10-1

D.

8.6 x 10

Correct answer is C

0.00043 x 2000

= 43 x 10-5 x 2 x 103

= 43 x 2 x 10-5+3

= 86 x 10-2

= 8.6 x 101 x 10-2

= 8.6 x 10-1

1,695.

A woman bought a grinder for N60,000. She sold it at a loss of 15%. How much did she sell it?

A.

N53,000

B.

N52,000

C.

N51,000

D.

N50,000

Correct answer is C

SP = Nx
CP = N60,000
Percentage loss = 15%
Using percentage loss...

\(\frac{CP - SP}{CP} = \text{100%}\)

\(\text{15%} = \frac{60000 - x}{60000} \times \text{100%}\)

\(\text{15%} \times 60000 = (60000 - x)\text{100%}\)

\(60000 - x = \frac{\text{15%} \times 60000}{\text{100%}}\)

60000 - x = 3 x 3000

60000 -x = 9000

x = 60000 - 9000

x = N51,000