WAEC Mathematics Past Questions & Answers - Page 18

86.

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

A.

4\(\frac{4}{7}\)

B.

2\(\frac{6}{7}\)

C.

2\(\frac{7}{9}\)

D.

4\(\frac{7}{9}\)

Correct answer is B

Error = 1.80 - 1.75 = 0.05

%error = \(\frac{error}{original length}\)

=  \(\frac{0.05 * 100}{1.75}\)

= 2.85 or  2\(\frac{6}{7}\)

87.

Three boys shared D 10,500.00 in the ratio 6:7:8. Find the largest share.

A.

4000

B.

5000

C.

4500

D.

3500

Correct answer is A

Total proportion is 6+7+8 = 21

\(\frac{6 * 10500}{21}\) = 3000

\(\frac{7 * 10500}{21}\) = 3500

\(\frac{8 * 10500}{21}\) = 4000

The largest share is 4000

88.

If a = 3 and b = -7, find the value of \(\frac{5b+(a+b)^2}{(a-b)^2}\)

A.

0.51

B.

0.91

C.

-0.19

D.

-0.51

Correct answer is C

 \(\frac{5b+(a+b)^2}{(a-b)^2}\)

= \(\frac{5 * -7 +(3+ -7)^2}{(3- -7)^2}\)

=  \(\frac{-35 + 16}{10^2}\)

=  \(\frac{-19}{100}\) or -0.19

89.

M varies directly as n and inversely as the square of p. If M= 3 when n = 2 and p = 1, find M in terms of n and p.

A.

\(\frac{3n}{2p^2}\)

B.

\(\frac{2n}{3p^2}\)

C.

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

D.

\(\frac{3n^2}{2p^2}\)

Correct answer is A

M = \(\frac{nk}{p^2}\) 

k →  \(\frac{mp^2}{n}\) =  \(\frac{3x1^2}{2}\)

k =  \(\frac{3}{2}\)

:  m = \(\frac{3xn}{2p^2}\)

90.

Find the 17term of the Arithmetic Progression (A.P):-6,-1,4

A.

-91

B.

-86

C.

74

D.

79

Correct answer is C

common difference d =  -1 - [-6] → -1 + 6

d = 5; a = -6

T\(_n\) = a + (n-1)d

: T\(_{17}\) = -6 + (17 - 1) 5 

→ -6 + (16)5

→ -6 + 80 = 74