WAEC Mathematics Past Questions & Answers - Page 72

356.

A straight line passes through the points P(1,2) and Q(5,8). Calculate the gradient of the line PQ

A.

\(\frac{3}{5}\)

B.

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

C.

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

D.

\(\frac{5}{3}\)

Correct answer is C

Let: (x1, y1) = (1, 2)

(x2, y2) = (5, 8)

The gradient m of \(\bar{PQ}\) is given by

m = \(\frac{y_2 y_1}{x_2 - x_1}\)

= \(\frac{8 - 2}{5 - 1}\)

= \(\frac{6}{4}\)

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

357.

The volume of a pyramid with height 15cm is 90cm3. If its base is a rectangle with dimension xcm by 6cm, find the value of x

A.

3

B.

5

C.

6

D.

8

Correct answer is A

Volume of pyramid = \(\frac{1}{3}\)lbh

90 = \(\frac{1}{3} \times x \times 6 \times 15\)

x = \(\frac{90 \times 33}{6 \times 15}\)

= 3

358.

The curve surface area of a cylinder, 5cm high is 110cm 2. Find the radius of its base. [Take \(\pi = \frac{22}{7}\)]

A.

2.6cm

B.

3.5cm

C.

3.6cm

D.

7.0cm

Correct answer is B

Curved surface area of cylinder = 2\(\pi\)rh

110 = 2 x \(\frac{22}{7}\) x r x 5

r = \(\frac{110 \times 7}{44 \times 5}\)

= 3.5cm

359.

Factorize; (2x + 3y)2 - (x - 4y)2

A.

(3x - y)(x + 7y)

B.

(3x + y)(2x - 7y)

C.

(3x + y)(x - 7y)

D.

(3x - y)(2x + 7y)

Correct answer is A

(2x + 3y)2 - (x - 4y)2

= (2x + 3y)(2x + 3y) - (x - 4y)(x - 4y)

= 4x2 + 12xy + 9y2 - (x2 - 8xy+ 16y2)

= 4x2 + 12xy + 19y2 - x2 + 8xy - 16y2

= 3x2 + 20xy - 7y2

= 3x2 + 21xy - xy - 7y2

= 3x(x + 7y) - y(x + 7y)

= (3x - y)(x + 7y)

360.

Make s the subject of the relation: P = S + \(\frac{sm^2}{nr}\)

A.

s = \(\frac{mrp}{nr + m^2}\)

B.

s = \(\frac{nr + m^2}{mrp}\)

C.

s = \(\frac{nrp}{mr + m^2}\)

D.

s = \(\frac{nrp}{nr + m^2}\)

Correct answer is D

P = S + \(\frac{sm^2}{nr}\)

P = S(1 + \(\frac{m^2}{nr}\))

P = S(1 + \(\frac{nr + m^2}{nr}\))

nrp = S(nr + m2)

S = \(\frac{nrp}{nr + m^2}\)