If clay cost $16.50 for 50lb how much does clay cost for 45 pounds

Ratio and propoertion or logic

ratio

cost:amount=16.5/50

16.5/50=x/45

times both sides by 50*45

16.5*45=50x

742.5=50x

divide both sides by 50

14.85=x

the answer is $14.85 for 45lb

or, math

16.5 for 50

1.65 for 5

50-5=45

16.5-1.65=14.85

answer is $14.85 for 45lb

45 divided by 50 = 90%

0.9*16.50=14.85