JAMB Mathematics Past Questions & Answers - Page 63

311.

If the angles of a quadrilateral are (3y + 10)°, (2y + 30)°, (y + 20)° and 4y°. Find the value of y.

A.

66°

B.

12°

C.

30°

D.

42°

Correct answer is C

Sum of angles in a quadrilateral = 360°

\(\therefore\) (3y + 10) + (2y + 30) + (y + 20) + 4y = 360

10y + 60 = 360 \(\implies\) 10y = 300

y = 30° 

312.

Find \(\frac{\mathrm d y}{\mathrm d x}\) if \(y = \cos x\).

A.

\(\sin x\)

B.

\(- \sin x\)

C.

\(\tan x\)

D.

\(- \tan x\)

Correct answer is B

If \(y = \cos x\)

\(\frac{\mathrm d y}{\mathrm d x}\) =—\(\sin x\)

313.

A man stands on a tree 150 cm high and sees a boat at an angle of depression of 74°. Find the distance of the boat from the base of the tree.

A.

52 cm

B.

43 cm

C.

40 cm

D.

15 cm

Correct answer is B

\(\tan 16 = \frac{x}{150}\)

\(x = 150 \tan 16\)

= \(43 cm\)

314.

A circular arc subtends angle 150° at the centre of a circle of radius 12cm. Calculate the area of the sector of the arc.

A.

30\(\pi\) cm\(^2\)

B.

60\(\pi\) cm\(^2\)

C.

120\(\pi\) cm\(^2\)

D.

150\(\pi\) cm\(^2\)

Correct answer is B

Area of sector = \(\frac{\theta}{360°} \times \pi r^{2}\)

= \(\frac{150}{360} \times \pi \times 12^{2}\)

= 60\(\pi\) cm\(^{2}\)

315.

If \(N = \begin{pmatrix} 3 & 5 & -4 \\ 6 & -3 & -5 \\ -2 & 2 & 1 \end{pmatrix}\), find \(|N|\).

A.

65

B.

23

C.

17

D.

91

Correct answer is C

\(\begin{vmatrix} 3 & 5 & -4 \\ 6 & -3 & -5 \\ -2 & 2 & 1 \end{vmatrix}\)

= \(3(-3 - (-10)) - 5(6 - 10) + (-4)(12 - 6)\)

= \(21 + 20 - 24\)

= 17