JAMB Mathematics Past Questions & Answers - Page 51

251.

In the diagram above, O is the centre of the circle ABC, < ABO = 26° and < BOC = 130°. Calculate < AOC.

A.

26°

B.

13°

C.

80°

D.

102°

Correct answer is D

< BAC = \(\frac{130}{2}\) (angle subtended at the centre)

< BAC = 65°

Also, x = 26° (theorem)

y = 65° - 26° = 39°

< AOC = 180° - (39° + 39°)

= 102°

252.

If \(P = (\frac{Q(R - T)}{15})^{\frac{1}{3}}\), make T the subject of the formula.

A.

\(T = \frac{15R - Q}{P^3}\)

B.

\(T = R - \frac{15P^3}{Q}\)

C.

\(T = \frac{R - 15P^3}{Q}\)

D.

\(T = \frac{R + P^3}{15Q}\)

Correct answer is B

\(P = (\frac{Q(R - T)}{15})^{\frac{1}{3}}\)

\(P^3 = \frac{Q(R - T)}{15}\)

\(Q(R - T) = 15P^3\)

\(R - T = \frac{15P^3}{Q}\)

\(T = R - \frac{15P^3}{Q}\)

253.

Points X and Y are 20km North and 9km East of point O, respectively. What is the bearing of Y from X? Correct to the nearest degree.

A.

24°

B.

56°

C.

127°

D.

156°

Correct answer is D

\(\tan \theta = \frac{9}{20} = 0.45\)

\(\theta = \tan^{-1} (0.45) \)

= 24.23°

\(\therefore\) The bearing of Y from X = 180° - 24.23°

= 155.77°

= 156° (to the nearest degree)

254.

Find the value of x and y in the simultaneous equation: 3x + y = 21; xy = 30

A.

x = 3 or 7, y = 12 or 8

B.

x = 6 or 1, y = 11 or 5

C.

x = 2 or 5, y = 15 or 6

D.

x = 1 or 5, y = 10 or 7

Correct answer is C

3x + y = 21 ... (i);

xy = 30 ... (ii)

From (ii), \(y = \frac{30}{x}\). Putting the value of y in (i), we have

3x + \(\frac{30}{x}\) = 21

\(\implies\) 3x\(^2\) + 30 = 21x

3x\(^2\) - 21x + 30 = 0

3x\(^2\) - 15x - 6x + 30 = 0

3x(x - 5) - 6(x - 5) = 0

(3x - 6)(x - 5) = 0

3x - 6 = 0 \(\implies\) x = 2.

x - 5 = 0 \(\implies\) x = 5.

If x = 2, y = \(\frac{30}{2}\) = 15;

If x = 5, y = \(\frac{30}{5}\) = 6.

255.

Simplify \(\frac{0.0839 \times 6.381}{5.44}\) to 2 significant figures.

A.

0.2809

B.

2.51

C.

3.5

D.

0.098

Correct answer is D

No explanation has been provided for this answer.