Using proportions, the estimate of the per capita consumption from 2011 was 29.25 gallons.
A proportion is a fraction of the total amount, the measures are related using a rule of three.
The amount in 2012 was an increase of 5.3% from 2011,
105.3% = 1.053 of x,
The consumption per capita was 30.8 gallons,
hence:
1.053x = 30.8
x = 30.8/1.053
x = 29.25 gallons.
(ii) The sales in 2011
= 9.1 billion gallons in 2011.
(iii) The per capita consumption from 2011
= 9.1 / 11.8
= 0.77 billion
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