JAMB Mathematics Past Questions & Answers - Page 413

2,061.

Find the principal which amounts to N5,500 at a simple interest in 5 years at 2% per annum.

A.

N4,900

B.

N5,000

C.

N4,700

D.

N4,800

Correct answer is B

Principal, P = Amount, A - Interest, I.
A = P + I

I = (P.T.R)/100 = (P x 5 x 2)/100 = 10P/100 = P/10

But A = P + I,
=> 5500 = P + (P/10)
=> 55000 = 10P + P
=> 55000 = 11P

Thus P = 55000/11 = N5,000

2,062.

If \(x = \frac{y}{2}\),evaluate\(\left(\frac{x^{3}}{y^{3}}+\frac{1}{2}\right) \div \left(\frac{1}{2} - \frac{x^{2}}{y^{2}}\right)\)

A.

5/8

B.

5/2

C.

5/32

D.

5/16

Correct answer is B

\(x = \frac{y}{2} \)

\(\left(\frac{x^{3}}{y^{3}}+\frac{1}{2}\right) \div \left(\frac{1}{2} - \frac{x^{2}}{y^{2}}\right)\)

\(\frac{x^3}{y^3} + \frac{1}{2} = (\frac{y}{2})^{3} \div y^{3} + \frac{1}{2}\)

= \(\frac{y^{3}}{8} \times \frac{1}{y^3} + \frac{1}{2}\)

= \(\frac{1}{8} + \frac{1}{2}\)

= \(\frac{5}{8}\)

\(\frac{1}{2} - \frac{x^2}{y^2} = \frac{1}{2} - (\frac{y}{2})^{2} \div y^2)\)

= \(\frac{1}{2} - \frac{y^2}{4} \times \frac{1}{y^2}\)

= \(\frac{1}{2} - \frac{1}{4}\)

= \(\frac{1}{4}\)

\(\therefore \left(\frac{x^{3}}{y^{3}}+\frac{1}{2}\right) \div \left(\frac{1}{2} - \frac{x^{2}}{y^{2}}\right) = \frac{5}{8} \div \frac{1}{4}\)

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

2,063.

A car dealer bought a second-hand car for N250,000 and spent N70,000 refurbishing it. He then sold the car for N400,000. What is the percentage gain?

A.

60%

B.

32%

C.

25%

D.

20%

Correct answer is C

Total cost = N(250,000 + 70,000) = N320,000
Selling price = N400,000 (given)
Gain = SP - CP = N(400,000 - 320,000) = N80,000
Gain % = gain/CP x 100 = (80,000/320,000) x 100

Gain % = 25%

2,064.

Given that \(p = 1 + \sqrt{2}\) and \(q = 1 - \sqrt{2}\), evaluate \(\frac{p^{2} - q^{2}}{2pq}\).

A.

2(2+√2)

B.

-2(2+√2)

C.

2√2

D.

-2√2

Correct answer is D

\(\frac{p^{2} - q^{2}}{2pq} = \frac{(p + q)(p - q)}{2pq}\)

= \(\frac{(1 + \sqrt{2} - (1 - \sqrt{2}))(1 + \sqrt{2} + 1 - \sqrt{2})}{2(1 + \sqrt{2})(1 - \sqrt{2})}\)

= \(\frac{(2\sqrt{2})(2)}{-2}\)

= \(-2\sqrt{2}\)

2,065.

Simplify \((\sqrt[3]{64a^{3}})^{-1}\)

A.

4a

B.

1/8a

C.

8a

D.

1/4a

Correct answer is D

\((\sqrt[3]{64a^{3}})^{-1} = (\sqrt[3]{(4a)^{3}})^{-1}\)

= \((4a)^{-1} \)

= \(\frac{1}{4a}\)