WAEC Mathematics Past Questions & Answers - Page 167

831.

\(\begin{array}{c|c} x & 1 & 4 & p \\ \hline y & 0.5 & 1 & 2.5\end{array}\). The table above satisfies the relation y = k\(\sqrt{x}\), where k is a positive constant. Find the value of K.

A.

0.5

B.

1

C.

1.5

D.

2

Correct answer is A

y = k\(\sqrt{x}\) when y = 1, x = 4

k = \(\frac{y}{\sqrt{x}}\)

= \(\frac{1}{\sqrt{4}}\)

= \(\frac{1}{2}\)

= 0.5

832.

The ratio of boys to girls in a class is 5:3. Find the probability of selecting at random, a girl from the class

A.

\(\frac{1}{8}\)

B.

\(\frac{1}{3}\)

C.

\(\frac{3}{8}\)

D.

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

Correct answer is C

ratio of boys to girls = 5:3

total = 5 + 3 = 8

Pr(girl) = \(\frac{3}{8}\)

833.

If tan y = 0.404, where y is acute, find cos 2y

A.

0.035

B.

0.719

C.

0.808

D.

0.927

Correct answer is B

tan y = 0.404; y = tan-1 0.0404(tables);y = 22o

cos 2y = cos 2(22o); cos 44o

= 0.719

834.

A baker used 40% of a 50kg bag of flour. If \(\frac{1}{8}\) of the amount used was for the cake, how many kilogram of flour was used for the cake?

A.

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

B.

6\(\frac{1}{2}\)

C.

15\(\frac{3}{8}\)

D.

17\(\frac{1}{2}\)

Correct answer is A

\(\frac{40}{100} \times 50\)kg = 20kg

\(\frac{1}{8}\) of 20kg for cake; \(\frac{1}{8}\) x \(\frac{20}{1}\)

= 2\(\frac{1}{2}\)kg

835.

If 30% of y is equal to x, what in terms of x, is 30% of 3y?

A.

\(\frac{x}{9}\)

B.

\(\frac{x}{3}\)

C.

x

D.

3x

Correct answer is D

If 30% of y = x, then 30% of 3y = 3x