JAMB Mathematics Past Questions & Answers - Page 153

761.

What is log7(49a) - log10(0.01)?

A.

\(\frac{49^a}{100}\)

B.

\(\frac{a}{2}\) + 2

C.

72a + 2

D.

2a + 2

E.

\(\frac{2a}{2}\)

Correct answer is D

log7(49a) - log10(0.01) = log7(72)a - log10100

log772a - log101 - log10 102

= 2a - 2

= 2a + a

762.

What is the greatest straight line distance between two vertices (corners) of a cube whose sides are 2239cm long?

A.

\(\sqrt{2239cm}\)

B.

\(\sqrt{2}\) x 2239cm

C.

\(\frac{\sqrt{3}}{2}\) 2239cm

D.

\(\sqrt{3}\) x 2239cm

E.

4478cm

Correct answer is D

x = \(\sqrt{-2239^2 + 2239^2}\)

= -\(\sqrt{10026242}\)

= 3166.42

y = -\(\sqrt{10026242 + 5013121}\)

= -\(\sqrt{15039363}\)

= 3878

= \(\sqrt{3}\) x 2239

763.

An arc of circle of radius 2cm subtends an angle of 60º at the centre. Find the area of the sector

A.

\(\frac{2 \pi}{3}\)cm2

B.

\(\frac{\pi}{2}\)cm2

C.

\(\frac{\pi}{3}\)cm2

D.

\(\pi\)cm2

Correct answer is A

Area of a sector \(\frac{\theta}{360}\) x \(\pi\)r\(^2\)

= \(\frac{60^o}{360^o}\) x \(\pi\)2\(^2\)

= \(\frac{2 \pi}{3}\)cm2

764.

A cylinder of height h and radius r is open at one end. Its surface area is

A.

2\(\pi\)rh

B.

\(\pi\)r2h

C.

2\(\pi\)rh + \(\pi\)r2

D.

2\(\pi\)rh + 2\(\pi\)r2

Correct answer is C

A cylinder of height h ans radius r is open at one end, its surface area is 2\(\pi\)rh + \(\pi\)r2

765.

Simplify \(\frac{1 - x^2}{x - x^2}\), where x \(\neq\) 0

A.

\(\frac{1}{x}\)

B.

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

C.

\(\frac{1 + x}{x}\)

D.

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

E.

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

Correct answer is C

\(\frac{1 - x^2}{x - x^2}\), where x = \(\neq\) 0

\(\frac{1^2 - x^2}{x - x^2}\)

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

= \(\frac{1 + x}{x}\)