WAEC Mathematics Past Questions & Answers - Page 168

836.

A fair coin is tossed three times. Find the probability of getting two heads and one tail.

A.

\(\frac{1}{2}\)

B.

\(\frac{3}{8}\)

C.

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

D.

\(\frac{1}{8}\)

Correct answer is B

Pr(head) = \(\frac{1}{2}\), Pr(tail) = \(\frac{1}{2}\):Pr(2 heads)

= \(\frac{1}{2}\) x \(\frac{1}{2}\) = \(\frac{1}{4}\)

Pr(2 heads and tail) 3 times

= (\(\frac{1}{4}\) x \(\frac{1}{2}\)) x 3

= \(\frac{3}{8}\)

837.

P is a point on the same plane with a fixed point A. If P moves such that it is always equidistant from A, the locus of P is

A.

a straight line joining A and P

B.

the perpendicular bisector of AP

C.

a circle with centre A

D.

the triangle with centre P

Correct answer is C

No explanation has been provided for this answer.

838.

Given that y = 1 - \(\frac{2x}{4x - 3}\), find the value of x for which y is undefined

A.

3

B.

\(\frac{3}{4}\)

C.

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

D.

-3

Correct answer is B

for undefined expression, the denomination is zero 4x - 3 = 0

4x = 3; x = \(\frac{3}{4}\)

839.

Simplify \(\frac{x - 4}{4} - \frac{x - 3}{6}\)

A.

\(\frac{x - 18}{12}\)

B.

\(\frac{x - 6}{12}\)

C.

\(\frac{x - 18}{24}\)

D.

\(\frac{x - 6}{24}\)

Correct answer is B

\(\frac{x - 4}{4} - \frac{x - 3}{6}\) = \(\frac{3(x - 4) - 2(x - 3)}{12}\)

= \(\frac{3x -12 - 2x + 6}{12}\)

= \(\frac{3x - 2x - 12 + 6}{12}\)

= \(\frac{x - 6}{12}\)

840.

Simplify \(\frac{25 ^\frac{2}{3} \div 25 ^\frac{1}{6}}{( \frac{1}{5})^{-\frac{7}{6}} \times ( \frac{1}{5})^{\frac{1}{6}}}\)

A.

25

B.

\(\frac{1}{5}\)

C.

1

D.

\(\frac{1}{25}\)

Correct answer is C

\(\frac{25 \frac{2}{3} \div 25 \frac{1}{6}}{( \frac{1}{5})^{-\frac{7}{6}} \times ( \frac{1}{5})^{\frac{1}{6}}}\) = \(\frac{25^{4 - \frac{1}{6}}}{(\frac{1}{5})^{-7 + \frac{1}{6}}}\)

= \(\frac{25^{\frac{1}{2}}}{(\frac{1}{5})^{-1}}\)

= \(\frac{(5^2)^{\frac{1}{2}}}{(5^{-1})^{-1}}\)

= \(\frac{5}{5}\)

= 1