WAEC Mathematics Past Questions & Answers - Page 95

471.

If 23x = 325, find the value of x

A.

7

B.

6

C.

5

D.

4

Correct answer is A

23x = 325

2 \(\times x^1 + 3 \times x^0 = 3 \times 5^1 + 2 \times 5^0\)

= 2x + 3 = 15 + 2

2x + 3 = 17

2x = 17 - 3

2x = 14

x = \(\frac{14}{2}\)

x = 7

472.

Simplify 10\(\frac{2}{5} - 6 \frac{2}{3} + 3\)

A.

6\(\frac{4}{15}\)

B.

6\(\frac{11}{15}\)

C.

7\(\frac{4}{15}\)

D.

7\(\frac{11}{15}\)

Correct answer is B

10\(\frac{2}{5} - 6 \frac{2}{3} + 3\)

\(\frac{52}{5} - \frac{20}{3} + \frac{3}{1}\)

= \(\frac{156 - 100 + 45}{15}\)

\(\frac{156 + 45 - 100}{15}\)

= \(\frac{201 - 100}{15}\)

= \(\frac{101}{15}\)

= 6\(\frac{11}{15}\)

473.

Using the venn diagram, find n(x \(\cap\) y1)

A.

2

B.

3

C.

4

D.

6

Correct answer is A

(x \(\cap\) y2) = [a, b]

n(x \(\cap\) y2) = 2

474.

In the diagram, ST//PQ reflex angle SRQ = 198o and < RQp = 72o. Find the value of y

A.

18o

B.

54o

C.

87o

D.

92o

Correct answer is B

R +198 = 360(angles at a point)

R = 360 - 198 = 162o

C = 72(alternate angle), b + c = 180(angles or straight line)

b = 190 - c = 180 - 72 = 108

a + b = R = 162

a = R - b = 162 - 108

= 54, but a = y(alternate angles)

y = 54o

475.

In the diagram, PQ is a straight line. Calculate the value of the angle labelled 2y

A.

130o

B.

120o

C.

110o

D.

100o

Correct answer is D

Sum of angles on straight line = 180o

80o + 50o + x + 10o = 180o

140o + x = 180o

x = 180o - 140o

x = 40o

total sum of all angles = 360o

2yo + 2xo + 80o + 50o + x + 10o = 360o

2yo + 2(40)o + 80o + 50o + 40 + 10 = 360o

2yo + 80 + 180o = 360o

2yo + 260o = 360o

2yo = 360o - 260o

2yo = 100o

angle 2yo = 100o