JAMB Mathematics Past Questions & Answers - Page 142

706.

In the diagram, angle QPR = 90o, angle PSR = 90o and PR = 5 units. Find the length of QS.

A.

5 tan 25o sin 65o

B.

5 cos 25o sin 65o

C.

5 tan 25o cos 65o

D.

cos 25o cos 65o

E.

5 cosec 25o

Correct answer is C

From \(\bigtriangleup\)QPR, < R = 180o - (25o + 90o)

180o - 115o = 65o

From \(\bigtriangleup\)PSQ, Sin 65o = \(\frac{QPR}{hyp}\) = \(\frac{PS}{5}\)

PS = 5 sin 65o

From \(\bigtriangleup\)PSR, tan = \(\frac{OPP}{adj}\) = \(\frac{PS}{QS}\)

but PS = 5 sin 65o

QS tan 25o = PS

QS tan 25o = 5 sin 65o

QS = \(\frac{5 sin 65^o}{tan 25^o}\)

= 5 tan 25o cos 65o

707.

In the figure, WU//YZ, WY//YZ = 12cm, VZ = 6cm, XU = 8cm. Determine the length of WU.

A.

1cm``3cm

B.

6cm

C.

2cm

D.

4cm

Correct answer is D

From similar triangle, \(\frac{x}{6}\) = \(\frac{8}{12}\)

12x = 48

x = \(\frac{48}{12}\)

= 4

708.

In the diagram, XZ is the diameter of a circle's radius \(\frac{5}{2}\). If XY is 4cm, then the area of the triangle XYZ is

A.

12cm2

B.

28\(\frac{1}{2}\)cm2

C.

16cm2

D.

10cm2

E.

6cm2

Correct answer is E

Area of the triangle XYZ = \(\frac{1}{2}\)bh = \(\frac{1}{2}\)ZY x XY

= \(\frac{1}{2}\) x 3 x 4

= 6cm2.

709.

In the figure, find x in terms of a, b and c.

A.

a + b + c

B.

180o - (a + b + c)

C.

a - b - c

D.

a + b

E.

a + c

Correct answer is A

180 - x + a + b + c

= 180(sum of interior angle in triangle)

a + b + c = x.

710.

In the figure, find the area of XYZW

A.

60cm2

B.

54cm2

C.

36cm2

D.

54\(\sqrt{2}\)cm2

E.

27\(\sqrt{2}\)cm2

Correct answer is C

Average of trapezium XYZW = \(\frac{1}{2}\)(a + b)h from rt < YDZ,

h = 8 sin 30º

area = \(\frac{1}{2}\)(10 + 8)4

= 8 x \(\frac{1}{2}\) = 4

\(\frac{1}{2}\)(18) x 4

= 36cm2