WAEC Mathematics Past Questions & Answers - Page 128

636.

How many times, correct to the nearest whole number, will a man run round circular track of diameter 100m to cover a distance of 1000m?

A.

3

B.

4

C.

5

D.

6

Correct answer is A

No. of times = \(\frac{\text{Total distance}}{\text{Circumference of circle}}\)

= \(\frac{\text{Total distance}}{\pi d}\)

= \(\frac{1000m}{\frac{22}{7} \times 100m}\)

= \(\frac{1000 \times 7}{2200} = 3.187\)

= 3(approx.) nearest whole no.

637.

The nth term of the sequence -2, 4, -8, 16.... is given by

A.

Tn = 2n

B.

Tn = (-2)n

C.

Tn = (-2n)

D.

Tn = n

Correct answer is B

sequence: -2, 4, -8, 16........{GP}

a = -2; r = \(\frac{4}{-2}\) = -2

nth term Tn = arn-1

Tn = (-2)(-2)^n-1

Tn = (-2)1 + n - 1

Tn = (-2)n

638.

If y = \(\frac{(2\sqrt{x^2 + m})}{3N}\), make x the subject of the formular

A.

\(\frac{\sqrt{9y^2 N^2 - 2m}}{3}\)

B.

\(\frac{\sqrt{9y^2 N^2 - 4m}}{2}\)

C.

\(\frac{\sqrt{9y^2 N^2 - 3m}}{2}\)

D.

\(\frac{\sqrt{9y^2 N - 3m}}{2}\)

Correct answer is B

y = \(\frac{(2\sqrt{x^2 + m})}{3N}\)

3yN = 2(\(\sqrt{x^2 + m})\)

\(\frac{3yN}{2} = \sqrt{x^2 + m}\)

(\(\frac{3yN}{2})^2 = ( \sqrt{x^2 + m})\)

\(\sqrt{\frac{9y^2N^2}{4} - \frac{m}{1}}\)

x = \(\frac{\sqrt{9Y^2N^2 - 4m}}{4}\)

x = \(\frac{\sqrt{9y^2N^2 - 4m}}{2}\)

639.

The sum of the exterior of an n-sided convex polygon is half the sum of its interior angle. find n

A.

6

B.

8

C.

9

D.

12

Correct answer is A

sum of exterior angles = 360o

Sum of interior angle = (n - 2) x 180

360 = \(\frac{1}{2}\) x(n - 2) x 180(90o)

360 = \(\frac{1}{2}\) x(n - 2) x 90o

\(\frac{360}{90}\) = a - 2

4 = n - 2

n = 4 + 2 = 6

640.

Simplify \(\frac{2}{2 + x} + \frac{2}{2 - x}\)

A.

\(\frac{4}{4 - x^3}\)

B.

\(\frac{8}{4 - x^2}\)

C.

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

D.

\(\frac{8 - 4x}{4 - x^2}\)

Correct answer is B

\(\frac{2}{2 + x} + \frac{2}{2 - x}\)

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

= \(\frac{8}{4 - x^2}\)