WAEC Mathematics Past Questions & Answers - Page 51

251.

Simplify the expression \(\frac{a^2 b^4 - b^2 a^4}{ab(a + b)}\)

A.

\(a^2 - b^2\)

B.

\(b^2 - a^2\)

C.

\(a^2b - ab^2\)

D.

\(ab^2 - a^2b\)

Correct answer is D

\(\frac{a^2 b^4 - b^2 a^4}{ab(a + b)}\) = \(\frac{a^2 b^24(b^2 - a^2}{ab(a + b)}\)

= \(\frac{ab [(b - a) (b + a)]}{a + b}\)

= ab(b - a)

= \(ab^2 - a^2b\)

252.

Three exterior angles of a polygon are 30\(^o\), 40\(^o\) and 60\(^o\). If the remaining exterior angles are 46\(^o\) each, name the polygon.

A.

decagon

B.

nonagon

C.

octagon

D.

hexagon

Correct answer is C

Sum of all exterior angles is 360\(^o\)

360\(^o\) (30\(^o\) - 40\(^o\))

360 - (130\(^o\))

230\(^o\)

remaining is 46\(^o\) = \(\frac{230}{46}\) = 5

5 + 3 = 8 sides; Octagon

253.

Simplify; \(\sqrt{2}(\sqrt{6} + 2\sqrt{2}) - 2\sqrt{3}\)

A.

4

B.

\(\sqrt{3} + 4\)

C.

4 \(\sqrt{2}\)

D.

4\(\sqrt{3} + 4\)

Correct answer is A

\(\sqrt{2}(\sqrt{6} + 2\sqrt{2}) - 2\sqrt{3}\)

\(\sqrt{12}\) + 2 x 2 - 2\(\sqrt{3}\)

2 \(\sqrt{3}\) - 2 \(\sqrt{3}\) + 4

= 4

254.

In what number base was the addition 1 + nn = 100, where n > 0, done?

A.

n - 1

B.

n + 1

C.

n

D.

n + 2

Correct answer is C

No explanation has been provided for this answer.

255.

The average age of a group of 25 girls is 10year. If one girl, aged 12 years and 4 months joins the group, find the new average age of the group

A.

10.1 years

B.

9.3 years

C.

8.7 years

D.

8 . 3 years

Correct answer is A

x = 10 ; 10 = \(\frac{x}{25}\)

x = 250

x = \(\frac{250 + 12.4}{26}\)

x = 10.09

x = 10.1 years