WAEC Mathematics Past Questions & Answers - Page 17

81.

Find the value of x such that \(\frac{1}{x}\) +\(\frac{4}{3x}\) - \(\frac{5}{6x}\) + 1 = 0

A.

\(\frac{1}{6}\)

B.

\(\frac{1}{4}\)

C.

\(\frac{-3}{2}\)

D.

\(\frac{-7}{6}\)

Correct answer is C

\(\frac{1}{x}\) +\(\frac{4}{3x}\) - \(\frac{5}{6x}\) + 1 = 0
using 6x as lcm

→ \(\frac{6+8-5+6x}{6x}\) 

→ \(\frac{9+6x}{6x}\) = 0

9+6x = 0

6x = -9

x = \(\frac{-9}{6}\)  or \(\frac{-3}{2}\)

82.

What value of p will make (x\(^2\) - 4x + p) a perfect square?

A.

-2

B.

16

C.

4

D.

-8

Correct answer is C

(x\(^2\) - 4x + p)

Use the coefficient of the middle variable(-4x)

= (\(\frac{-4}{2}\))\(^2\)

= (-2)\(^2\)

= 4

83.

Consider the statements:

p: Stephen is intelligent

q: Stephen is good at Mathematics

If p⇒q, which of the following is a valid conclusion?

A.

If Stephen is good at Mathematics, then he is intelligent

B.

If Stephen is not good at Mathematics, then he is not intelligent

C.

If Stephen is not intelligent, then he is not good at Mathematics

D.

If Stephen is not good at Mathematics, then he is intelligent

Correct answer is B

If p implies (→) q

then not (~) q → not (~) p

Option B

84.

Mary has $ 3.00 more than Ben but $ 5.00 less than Jane. If Mary has $ x, how much does Jane and Ben have altogether?

A.

$(2x-8)

B.

$(2x+8)

C.

$(2x-2)

D.

$(2x+2)

Correct answer is D

Mary(m), Ben(b) Jane(j) m = b +3 m = j - 5 where m = x b = x - 3 and j = x + 5 b+ j → x - 3 + x + 5 = 2x +2 Jane and Ben have $(2x+2)

85.

If 5x + 3y=4 and 5x-3y= 2, what is the value of (25x\(^2\) -9y\(^2\))?

A.

20

B.

16

C.

2

D.

8

Correct answer is D

5x + 3y=4

5x-3y= 2

Using elimination method 

5x + 3y=4 →    5x + 3y=4

-[5x-3y= 2] → -5x +3y= -2

6y = 2 

y → 1/3 and x = 3/5

solving (25x\(^2\) -9y\(^2\))

25 * [3/5]\(^2\) -9 * [1/3]\(^2\)

25 * \(\frac{9}{25}\) - 9 \(\frac{1}{9}\)

9 - 1 = 8