SOLUTION: The perimeter of a small rectangular house is 120 yards. Carrie wrote a function B(l) that represents the area of the house with length l. Find her mistake, explain where she went

Question 1010117: The perimeter of a small rectangular house is 120 yards. Carrie wrote a function B(l) that represents the area of the house with length l. Find her mistake, explain where she went wrong, and correct her mistakes. I do not know how to start in the first place, I tried figuring it out by rereading the question and look at the problem. I just got confused.
2l+2w=120
w=120-2l
A=lw
B(l)=l(120-2l)
B(l)=120l-21^2
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39630) (Show Source): You can put this solution on YOUR website!
Characters chosen for writing variables for written communication is important.
2l+2w=120
Twenty one plus two w equals one hundred twenty

w=120-2l
w is equal to one hundred twenty minus twenty one

Carrie needs to choose variables more carefully. Typewritten text does not have the flexibility that manually written characters can have.
Answer by MathTherapy(10557) (Show Source): You can put this solution on YOUR website!

The perimeter of a small rectangular house is 120 yards. Carrie wrote a function B(l) that represents the area of the house with length l. Find her mistake, explain where she went wrong, and correct her mistakes. I do not know how to start in the first place, I tried figuring it out by rereading the question and look at the problem. I just got confused.
2l+2w=120
w=120-2l
A=lw
B(l)=l(120-2l)
B(l)=120l-21^2

2l + 2w = 120
w=120-2l <------- ERROR
2w = 120 - 2l <----- Previous equation should be this. This leads to:

As lower case l looks a lot like the number 1, it's best to use upper case l (L) to denote the length
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