JAMB Mathematics Past Questions & Answers - Page 61

301.

In the figure, PQRS is a rectangle. If the shaded area is 72 sq. cm, find h.

A.

12cm

B.

10cm

C.

8cm

D.

5cm

Correct answer is D

From the diagram, PQRS is a rectangle

Area of shaded part = 72sq.cm

But 72 = 3h - 4 + 6h - 4 + 4h

= 72 - 16h - 8

= 16h - 72 + 8

=16h = 80

h = \(\frac{80}{16}\)

= 5cm

302.

Solve \(5^{2(x - 1)} \times 5^{x + 1} = 0.04\)

A.

\(\frac{1}{3}\)

B.

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

C.

\(-\frac{1}{5}\)

D.

\(-\frac{1}{3}\)

Correct answer is D

\(5^{2(x - 1)} \times 5^{x + 1} = 0.04\)

\(5^{2x - 2} \times 5^{x + 1} = 5^{-2}\)

\(2x - 2 + x + 1 = -2\)

\(3x - 1 = -2 \implies 3x = -2 + 1 = -1\)

\(x = -\frac{1}{3}\)

303.

Subtract 16418\(_9\) from 18630\(_9\).

A.

1121\(_9\)

B.

2112\(_9\)

C.

2113\(_9\)

D.

2211\(_9\)

Correct answer is D

18630\(_9\) - 16418\(_9\) = 2211\(_9\)

305.

Given that y varies inversely as the square of x. If x = 3 when y = 100, find the equation connecting x and y.

A.

\(yx^2 = 300\)

B.

\(yx^2 = 900\)

C.

y = \(\frac{100x}{9}\)

D.

\(y = 900x^2\)

Correct answer is B

Y \(\alpha \frac{1}{x^2} \rightarrow y = \frac{k}{x^2}\)

If x = 3 and y = 100,

then, \(\frac{100}{1} = \frac{k}{3^2}\)

\(\frac{100}{1} = \frac{k}{9}\)

k = 100 x 9 = 900

Substitute 900 for k in

y = \(\frac{k}{x^2}\); y = \(\frac{900}{x^2}\)

= \(yx^2 = 900\)