WAEC Mathematics Past Questions & Answers - Page 11

51.

Solve 6x\(^2\) = 5x - 1

A.

x = 2,3

B.

x = 0,3

C.

x = \(\frac{1}{2}\), \(\frac{1}{3}\)

D.

x = \(\frac{1}{2}\), \(\frac{-1}{3}\)

Correct answer is C

6x\(^2\) = 5x - 1

 → 6x\(^2\) - 5x + 1 = 0

Factorization:

factors are -3x and -2x

6x\(^2\) - 3x  -2x  + 1 = 0

(6x\(^2\) - 3x) (-2x  + 1) = 0

3x(2x-1) -1(2x-1) = 0

(3x-1) (2x-1) = 0

x = \(\frac{1}{2}\), \(\frac{1}{3}\)

52.

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

53.

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

54.

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

55.

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