WAEC Mathematics Past Questions & Answers - Page 166

826.

A machine valued at N20,000 depreciates by 10% every year. What will be the value of the machine at the end of two years?

A.

N16,200

B.

N1,4,200

C.

12,000

D.

8000

Correct answer is A

D = P(I - \(\frac{R}{100}\))n where P = N20,000; R = 10%, n = 2

D = 20,000(I - \(\frac{10}{100}\))2

= 20000(0.9)2

20,000 x 0.81 = N16,200

827.

What is the place value of 9 in the number 3.0492?

A.

\(\frac{9}{10000}\)

B.

\(\frac{9}{1000}\)

C.

\(\frac{9}{100}\)

D.

\(\frac{9}{10}\)

Correct answer is B

Place value of 9 in 3.0492

= 0.009

= \(\frac{9}{1000}\)

828.

Given that (2x - 1)(x + 5) = 2x2 - mx - 5, what is the value of m

A.

11

B.

5

C.

-9

D.

-10

Correct answer is C

(2x - 1)(x + 5) = 2x2 - mx - 5

2x2 + 10x - x - 5

= 2x2 + 9x - 5 = 2x2 - mx - 5

comparing the co-efficient of x

-m = 9

m = -9

829.

What must be added to x2 - 3x to make it a perfect square?

A.

\(\frac{9}{4}\)

B.

\(\frac{9}{2}\)

C.

6

D.

9

Correct answer is A

x2 - 3x + k(perfect square)

k = (-\(\frac{3}{2}\))2 ; k = \(\frac{9}{4}\)

830.

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

A.

2

B.

4

C.

10

D.

25

Correct answer is D

From y = \(\frac{1}{2} \sqrt{x}\)

when y = 2.5 or \(\frac{5}{2}\), x = P

\(\frac{5}{2} \times \frac{1}{2} \sqrt{P}\)

\(\sqrt{P} = \frac{10}{2} = 5\)

P = 52

= 25