WAEC Mathematics Past Questions & Answers - Page 163

811.

A ladder 16m long leans against an electric pole. If the ladder makes an angle of 65o with the ground, how far up the electric pole does its top reach

A.

6.8m

B.

14.5m

C.

17.7m

D.

34.3m

Correct answer is B

Sin 65o = \(\frac{x}{16}\)

x = 16x sin 65

= 16 x 0.9063

x = 14.5m

812.

Simplify \(\frac{20}{5\sqrt{28} - 2 \sqrt{63}}\)

A.

\(\frac{5\sqrt{7}}{7}\)

B.

\(\frac{5\sqrt{5}}{7}\)

C.

\(\frac{7\sqrt{5}}{7}\)

D.

\(\frac{7\sqrt{7}}{5}\)

Correct answer is A

\(\frac{20}{5 \sqrt{4 \times 7} - 2\sqrt{9 \times 7}}\)

\(\frac{20}{10 \sqrt{7} - 6\sqrt{7}}\)

= \(\frac{20 \sqrt{7}}{4 \sqrt{7}}\)

= \(\frac{5\sqrt{7}}{7}\)

813.

The temperature in a chemical plant was -5oC at 2.00 am. The temperature fell by 6oC and then rose again by 7oC. What was the final temperature?

A.

-6oC

B.

-4oC

C.

4oC

D.

8oC

Correct answer is B

Temperature = -5oC

It fell by 6oC = -5oC - 6oC

= -11oC

Then rose by 7oC = -11 + 7

= -4oC (final temperature)

814.

Which of the following is not a measure of centre tendency?

A.

mean

B.

mode

C.

range

D.

median

Correct answer is C

No explanation has been provided for this answer.

815.

A rectangular carpet 2.5m long and 2.4m wide covers 5% of a rectangular floor. Calculate the area of the floor

A.

30m2

B.

57m2

C.

120m2

D.

225m2

Correct answer is C

Area of carpet = 2.5 x 2.4 = 6

Let F represent the floor

6 = 5% of F

6 = \(\frac{5}{100}\) x F

5F = 6 x 100

F = 6 x \(\frac{100}{5}\)

= 120m2