WAEC Mathematics Past Questions & Answers - Page 130

646.

\(\begin{array}{c|c} \text{No. of pets} & 0 & 1 & 2 & 3 & 4 \\ \hline \text{No. of students} & 8 & 4 & 5 & 10 & 3\end{array}\) The table shows the number of pets kept by 30 students in a class. If a student is picked at random ftom the class. What is the probability that he/she kept more than one pet?

A.

\(\frac{1}{5}\)

B.

\(\frac{2}{5}\)

C.

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

D.

\(\frac{4}{5}\)

Correct answer is C

pr. (More than one pet)

= \(\frac{\text{No. of students with > 1 pet}}{\text{total no. of students}}\)

= \(\frac{5 + 10 + 3}{30}\)

= \(\frac{18}{30}\)

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

647.

Given that \(\frac{5^{n +3}}{25^{2n -3}}\) = 5º, find n

A.

n = 1

B.

n = 2

C.

n = 3

D.

n = 5

Correct answer is C

\(\frac{5^{n +3}}{25^{2n -2}}\) = 5o

\(\frac{5^{n + 3}}{5^{2(2n - 3)}}\) = 5o

n + 3 - 4n + 6 = 0

-3n + 9 = 0

-3n = -9

n = \(\frac{-9}{-3}\)

n = 3

648.

An empty rectangular tank is 250cm long and 120cm wide. If 180 litres of water is poured into the tank. Calculate the height of the water

A.

6.0cm

B.

5.5cm

C.

5.0cm

D.

4.5cm

Correct answer is A

Volume of water in tank = l x b x h = 180 litres

but 1 litre = 1000cm2

250 x 120 x hw = 180 x 1000

hw = \(\frac{180 \times 1000}{250 \times 120}\)

= 6cm

649.

Solve the inequality: 3(x + 1) \(\leq\) 5(x + 2) + 15

A.

x \(\geq\) -14

B.

x \(\leq\) - 14

C.

x \(\geq\) -11

D.

x \(\leq\) - 11

Correct answer is C

3(x + 1) \(\leq\) 5(x + 2) + 15

3x + 3 \(\leq\) 5x + 10 + 15

3x - 5x \(\leq\) 10 + 15 - 3

-2x \(\leq\) 22

x \(\geq\) \(\frac{-22}{2}\)

x \(\geq\) -11

650.

Given that = {x: -2 < x \(\leq\) 9}, where x is an integer what is n(T)?

A.

9

B.

10

C.

11

D.

12

Correct answer is C

T = {-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

n(T) = 11