Sam is building a new deck. His decking material is sold by the square foot. At a cost of $3.90 per square foot, how much will it cost Sam to build a deck that is 18 feet by 14 feet?
When you are solving word problems, look at the units and key words. Here the units are dollars ($) and square feet (feet x feet). One key word in this problem is the word "by". By when used here, it means multipy. So replace the word "by" with a multiplication symbol. This gives us: 18 feet x 14 feet Which we can write as 252 square feet. So what do we know? Well we know that decking costs $3.90 per square feet. So for every square foot of decking we need, it will cost us $3.90. We could add $3.90 for every square piece of decking we need. We need 252 of them. However, since multiplication is just fast way to add the same number over and over again. It's much easier to multiply. So multiply $3.90 times 252. We get $982.80
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