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WAEC Mathematics Past Questions & Answers - Page 218

1,086.

A boy estimated his transport fare for a journey as N190 instead of N200. Find the percentage error in his estimate

95%

47.5%

5.26%

Correct answer is D

The percentage error is $\frac{error}{actual}\times \frac{100}{1}\%\\ =\frac{200-190}{200}\times \frac{100}{1}\\ =\frac{10}{200}\times \frac{100}{1}\% = 5\%$

1,087.

In a bag of oranges, the ratio of the good ones to the bad ones is 5:4. If the number of bad oranges in the bag is 36, how many oranges are there in the altogether?

View answer & explanation

Correct answer is A

Ratio of good ones to bad ones is 5:4; If 36 is bad;

∴ the good ones = $\frac{5\times 36}{4}=45$ oranges.

The total number of oranges is 36 + 45 = 81.

1,088.

If N varies directly as M and N = 8 when M = 20 find M when N = 7

$17\frac{1}{2}$

$18\frac{1}{2}$

View answer & explanation

Correct answer is C

N ∝ M
∴N = kM where k is a constant
N = 8 when M = 20
∴ 8 = k x 20
$k = \frac{8}{20} = \frac{2}{5}\\ ∴ N = \frac{2}{5}M\\ If N = 7\\ ∴ 7 = \frac{2}{5}M\\ M = \frac{35}{2} = 17\frac{1}{2}$

1,089.

In a class of 80 students, every students studies Economics or Geography or both. If 65 students study Economics and 50 study Geography, how many study both subjects?

View answer & explanation

Correct answer is C

Let c = no of students that offered both subjects ∴ No of students offering Economics = 65 - c No of students offering Geography = 50 - c 65 - c + c + 50 - c = 80 115 - c = 80 c = 35 35 students offer both Economics and Geography.

1,090.

Evaluate $log_{10}5 + log_{10}20$