Percentage increase and decrease - Jamb Mathematics Past Questions and Answers

Question 1:

• JAMB 1979

The mean of the numbers 1.2, 1.0, 0.9, 1.4, 0.8, 0.8, 1.2 and 1.1 is

A. 1.5
B. 0.8
C. 1.0
D. 1.02
E. 1.05

Question 2:

• JAMB 1978

Father reduced the quantity of food bought for the family by 10% when he found that the cost of living had increased 15%. Thus the fractional increase in the family food bill is now

A. \(\frac{1}{12}\)
B. \(\frac{6}{35}\)
C. \(\frac{19}{300}\)
D. \(\frac{7}{200}\)
E. \(\frac{5}{100}\)

Question 3:

• JAMB 1979

The size of a quantity first doubles and then increases by a further 16%. After a short time its size decreases by 16%. What is the net increases in size of the quantity?

A. \(\frac{59300}{625}\)
B. \(\frac{50900}{625}\)
C. 200%
D. +100%