Question

an engineer estimates that 30% of gasoline is used efficiently by a car. how many gallons,out of 20 gallons, are used efficiently?

Answer 1

We need to find 30% of 20 gallons.

1) We can write a proportion

20 gallons ---- 100%

x gallons --------30%

x = 20*30/100 = 6 gallons

2) Or we can write 30% as decimal.

30% = 30/100 = 0.3

0.3 of 20 = 0.3*20 =6 gallons

Answer 6 gallons are used efficiently.