SOLUTION: This has me so confussed! Mary knows that a used Biology book may costs about half as much as a new one. She bought a used Biology Book for $90.00. Which equation could be us

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Question 612114: This has me so confussed!
Mary knows that a used Biology book may costs about half as much as a new one. She bought a used Biology Book for $90.00. Which equation could be used to find P, the price of Mary's book if she had bought a new one?
A.) p - 1/2 = 90 B.) p = 1/2 x 90 c.) 2p = 90 D.) p/2 = 90
Could you please help and explain!
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Let P = price of a new book

Since "Mary knows that a used Biology book may costs about half as much as a new one", this means that we can say

Price of Used Book = Half of Price of New Book

But we know that the price of a used book is $90, so we can replace the left side to get

90 = half of price of new book

Now we can replace the right side with P/2 since this represents cutting the price of a new book in half (cutting something in half or dividing by 2 is the same thing)

So we now have

90 = P/2

Finally, we can flip the equation to get


P/2 = 90


So the answer is choice D
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