WAEC Mathematics Past Questions & Answers - Page 120

596.

The length of a piece of stick is 1.75m. A girl measured it as 1.80m. Find the percentage error

A.

\(\frac{28}{7}\)%

B.

\(\frac{29}{7}\)%

C.

5%

D.

\(\frac{20}{7}\)%

Correct answer is D

Error = 1.80m - 1.75m = 0.05m

%error = \(\frac{\text{error}}{\text{true measurement}}\) x 100%

597.

The perimeter of a sector of a circle of radius 4cm is (\(\pi + 8\))cm. Calculate the anle of the sector

A.

45o

B.

60o

C.

75o

D.

90o

Correct answer is A

Perimeter of sector = 2r + \(\frac{\theta}{360^o} \times 2\pi r\)

\(\pi + 8 = 2 \times 4 + \frac{\theta}{3360^o} \times 2 \pi \times 4\)

\(\pi + 8 + \frac{\theta}{360^o} \times 8 \pi\)

P + 8 - 8 = \(\frac{\theta \pi}{456o}\)

\(\pi = \frac{\theta \pi}{45^o}\)

\(\theta \pi = 45^o\)

598.

Which of these angles can be constructed using ruler and a pair of compasses only?

A.

115o

B.

125o

C.

135o

D.

145o

Correct answer is C

No explanation has been provided for this answer.

599.

Simplify \(\frac{\log \sqrt{27}}{\log \sqrt{81}}\)

A.

3

B.

2

C.

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

D.

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

Correct answer is D

\(\frac{\log \sqrt{27}}{\log \sqrt{81}}\) = \(\frac{\log 27\frac{1}{2}}{81\frac{1}{2}}\)

= \(\frac{\log 3\frac{1}{2}}{\log 3^2}\)

\(\frac{\frac{3}{2} \log 3}{2 \log 3} = \frac{3}{2} \div \frac{2}{1}\)

= \(\frac{3}{2} \times \frac{1}{2}\)

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

600.

From the equation whose roots are x = \(\frac{1}{2}\) and -\(\frac{2}{3}\)

A.

6x2 - x + 2 = 0

B.

6x2 - x - 2 = 0

C.

6x2 + x + 2 = 0

D.

6x2 + x - 2 = 0

Correct answer is D

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

expand (x - \(\frac{1}{2}\))(x + \(\frac{2}{3}\)) = 0

x(x + \(\frac{2}{3}\)) - \(\frac{1}{2}(x + \frac{2}{3}\)) = 0

x2 + \(\frac{4x - 3x}{6} - \frac{2}{6} = 0\)

\(x^2 + \frac{x}{6} - 2 = 0\)

6x2 + x - 2 = 0