WAEC Mathematics Past Questions & Answers - Page 11

51.

Given that log\(_3\) 27 = 2x + 1, find the value of x.

A.

0

B.

1

C.

2

D.

3

Correct answer is B

Recall that: log\(_3\) 27 → log\(_3\)3\(^3\)

3log\(_3\)3 → 3 * 1

= 3

Then log\(_3\) 27 = 2x + 1

→ 3 = 2x + 1 

3 - 1 = 2x

2 = 2x

1 = x

52.

A trader made a loss of 15% when an article was sold. Find the ratio of the selling price : cost price

A.

3:20

B.

3:17

C.

17:20

D.

20:23

Correct answer is C

Where the loss= (100-15)%

= 85%

Ratio = 85:100 or 17:20

53.

If the equations x\(^2\) - 5x + 6 = 0 and x + px + 6 = 0 have the same roots, find the value of p.

A.

5

B.

6

C.

-5

D.

-6

Correct answer is C

If "x" is the same for both equations, then they are equivalent.

 (i.e., the equations have same roots), then the equations are equivalent.

Then p = -5

54.

The straight line y = mx - 4 passes through the point(-4,16). Calculate the gradient of the line

A.

-5

B.

-3

C.

3

D.

5

Correct answer is A

where x=-4 and y = 16, 
16 = -4m - 4
4m = -16 - 4
4m = -20
M = -5

55.

The mean of two numbers x and y is 4. Find the mean of four numbers x, 2x, y and 2y

A.

2

B.

4

C.

6

D.

8

Correct answer is C

Since the mean of the two numbers x and y is:

\(\frac{x+y}{2}\) = 4

 x+y =2 * 4

x+y = 8

then we get:

\(\frac{x+2x+y+2y}{4}\)

=(\(\frac{3x+3y}{4}\))

= 3(\(\frac{x+y}{4}\)) → 3(\(\frac{8}{4}\)) 

= 3 * 2

= 6