Processing math: 70%

JAMB Mathematics Past Questions & Answers - Page 170

846.

The area of a circular plate is one-sixteenth the surface area of a ball. If the area of the plate is given as P cm², then the radius of the ball is

A.

2Pπ

B.

Pπ

C.

P2π

D.

2Pπ

Correct answer is D

Surface area of a sphere = 4πr2

116 of 4πr2

= πr24

P = πr24

r = 2Pπ

847.

The difference between the length and width of a rectangle is 6cm and the area is 135cm². What is the length?

A.

25cm

B.

18cm

C.

15cm

D.

24cm

E.

27cm

Correct answer is C

Area = L x B

L - B = 6

L = 6 + B

area = 135

B(6 + B) = B2 + 6B - 135 = 0

B = 9

L = 6 + 9

= 15

848.

The positive root of t in the following equation, 4t2 + 7t - 1 = 0, correct to 4 places of decimal, is

A.

1.0622

B.

10.6225

C.

0.1328

D.

0.3218

E.

2.0132

Correct answer is C

4t2+7t1=0

Using a = 4, b = 7, c = -1.

x=b±b24ac2a

= 7±724(4)(1)2(4)

= 7±49+168

= 7±658

= 7±8.06238

The positive answer = 7+8.06238=1.06238

(4 decimal place)

849.

Evaluate \frac{6.3 \times 10^5}{8.1 \times 10^3} to 3 significant fiqures

A.

77.80

B.

778.0

C.

7.870

D.

8.770

E.

88.70

Correct answer is A

\frac{6.3 \times 10^5}{8.1 \times 10^3}

\frac{7}{9} \times 10^{2}

= 0.77778 \times 10^{2}

= 77.778 \approxeq 77.80

850.

The number 25 when converted from the tens and units base to the binary base (base two) is one of the following

A.

10011

B.

111011

C.

111000

D.

11001

E.

110011

Correct answer is D

\begin{array}{c|c} 2 & 25\\2 & 12 R 1\\2 & 6 R 0\\2 & 3 R 0\\2 & 1 R 1\end{array}

= (11001)