WAEC Mathematics Past Questions & Answers - Page 127

631.

The subtraction below is in base seven. Find the missing number.
5 1 6 2seven
-2 6 4 4seven
--------
2 * 1 5
--------

A.

2

B.

3

C.

4

D.

5

Correct answer is A

5 1 6 2seven
-2 6 4 4seven
--------
2 2 1 5
--------

the missing number is 2

632.

What is the value of x when y = 5?

y = \(\frac{1}{2}\)  x + 1

A.

8

B.

9

C.

10

D.

11

Correct answer is A

when y = 5; x = ?; y = \(\frac{1}{2}\)x + 1

5 = \(\frac{1}{2}\)x + 1

5 - 1 = \(\frac{1}{2}\)x

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

x = 4 x 2

x = 8

633.

\(\begin{array}{c|c} x & 0 & 2 & 4 & 6\\ \hline y & 1 & 2 & 3 & 4\end{array}\).
The table is for the relation y = mx + c where m and c are constants. What is the equation of the line described in the tablet?

A.

y = 2x

B.

y = x + 1

C.

y = x

D.

y = \(\frac{1}{2}x + 1\)

Correct answer is D

y = mx + c; when x = 0; y = 1

1 = m(0) + c; 1 = 0 + c; c = 1

when x = 2; y = 2

2 = m(2) + c; 2 = 2m + c; but c = 1

2 = 2m + 1

2 - 1 = 2m

2m = 1

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

y = \(\frac{1}{2}\)x + 1

634.

The mean age of R men in a club is 50 years, Two men aged 55 and 63, left the club and the mean age reduced by 1 year. Find the value of R

A.

18

B.

20

C.

22

D.

28

Correct answer is B

mean age = \(\frac{\text{sum of ages}}{\text{no. of men}}\)

50 = \9\frac{sum}{R}\)

sum = 50R.....(1)

Sum of ages of the men that left = 55 + 63 = 188

remaining sum = 50R - 118

remaining no. of men = R - 2

now mean age = 50 - 1 = 49 years

49 = \(\frac{50R - 118}{R - 2}\)

49(R - 2) = 50R - 118

49R - 50R = -188 - 98

-R = -20

R = 20

635.

Bola sold an article for N6,900.00 and made a profit of 15%. If he sold it for N6,600.00 he would make a

A.

profit of 13%

B.

loss of 12%

C.

loss of 10%

D.

loss of 5%

Correct answer is C

s.p = N6900

%profit = 15%

%profit = \(\frac{s.p - c.p}{c.p}\) x 100%

15% = \(\frac{6900 - c.p}{c.p}\) x 100%

\(\frac{15}{100}\)c.p = N6900 - c.p

0.15 c.p = N6900 - c.p

1.15c.p + c.p = N6900

c.p = \(\frac{6900}{1.15}\)

= 6000.00

Now new S.P = N6600

profit = s.p - c.p = 6000 - 6600

= 600

%profit = \(\frac{600}{6600}\) x 100%

= 10%