WAEC Mathematics Past Questions & Answers - Page 194

966.

From the Venn diagram below, how many elements are in P∩Q?

A.

1

B.

2

C.

4

D.

6

Correct answer is B

P \(\cap\) Q = {f, e} = 2

967.

If \(P = \sqrt{QR\left(1+\frac{3t}{R}\right)}\), make R the subject of the formula.

A.

\(R = \frac{3Qt}{P^2 - Q}\)

B.

\(R = \frac{P^2 – 3t}{Q+1}\)

C.

\(R = \frac{P^2 + 3t}{Q - 1}\)

D.

\(R = \frac{P^2-3Qt}{Q}\)

Correct answer is D

No explanation has been provided for this answer.

968.

In a ∆ XYZ, /YZ/ = 6cm YXZ = 60o and XYZ is a right angle. Calculate /XZ/in cm, leaving your answer in surd form

A.

2√3

B.

4√3

C.

6√3

D.

12√3

Correct answer is B

\(sin \theta = \frac{opp}{hyp}\\
sin 60^o = \frac{|YZ|}{|XZ|}=\frac{6}{P}\\
P sin 60^o = 6\\
P = \frac{6}{sin60^o}\\
=\frac{6}{\sqrt{\frac{3}{2}}}=4\sqrt{3}\)

969.

Which of the following is/are not the interior angle(s) of a regular polygon?

I.108° 
II. 116°
III. 120°

A.

I only

B.

II only

C.

III only

D.

I and III only

Correct answer is B

Using the formula, \((n - 2) \times 180°\) to get the sum of the interior angles. Then we can have

\((n - 2) \times 180° = 108n\) ... (1)

\((n - 2) \times 180° = 116n\) ... (2)

\((n - 2) \times 180° = 120n\) ... (3)

Solving the above given equations, where n is not a positive integer then that angle is not the interior for a regular polygon.

(1): \(180n - 360 = 108n \implies 72n = 360\)

 \(n = 5\) (regular pentagon)

(2): \(180n - 360 = 116n \implies 64n = 360\)

 \(n = 5.625\)

(3): \(180n - 360 = 120n \implies 60n = 360\)

 \(n = 6\) (regular hexagon)

Hence, 116° is not an angle of a regular polygon.

970.

If \(\frac{3^{(1-n)}}{9^{-2n}}=\frac{1}{9}\) find n

A.

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

B.

\(\frac{1}{3}\)

C.

-1

D.

-3

Correct answer is C

\(\frac{3^{(1-n)}}{9^{-2n}}=\frac{1}{9}\\
3^{1-n}\times 3^{-2(-2n)} = 3^{-2}\\
1-n-2(-2n)= -2\\
1-n+4n=-2\\
n=-1\)