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So, lets say it costs 1.25 per square yard to paint a wall. The wall is 18x25 feet.

How much will it cost to paint the wall.

First, I don't understand what is better. Converting 18x25 feet into yards which is (54x75) or converting down the cost from yard to feet which is aprox 0.416.

But lets say that it's better to convert feet to yards in this situation.

X is the cost.

X=((54*75)/9)*1.25

But again. There are 3 feet in a yard, and it looks like that 9 is squared. But I fail to understand why it's that way.

Can anyone explain? Thanks!

  • 2
    Dimensional analysis (i.e., "check your units") is a good idea even in mathematics.2011-05-20

1 Answers 1

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The wall is not 18 x 25 feet. The wall is 18 feet x 25 feet, which is 18 x 25 square feet.

Converting 18 x 25 square feet into square yards does not give 54 x 75 square yards. Yards are bigger than feet. 18 feet, that's not 54 yards, it's 6 yards. 18 x 25 square feet give 6 x (25/3) square yards.

So the cost is 6 x (25/3) x $1.25, whatever that comes to.