Sally and Mike are both selling books. Each of them will earn $2 per book sold plus an additional $4 if they sell more than 10 books.
Sally sold 11 books and Mike sold 22 books.
The money they will earn, if they sell more than 10 books, is represented by the equation m = 2b+4 , where b represents the number of books sold, and m represents the money they will earn.
Mike incorrectly determined that he earned twice as much as Sally. Each step of his work is shown in the table below.
Steps Mike's Work
1 For Sally b = 11
2 For Sally m = 2(11) + 4
3 For Mike b = 22
4 For Mike m = 2(22 + 4)
In which step did Mike make an error?
A.
Step 1
B.
Step 2
C.
Step 3
D.
Step 4
The correct equation to determine the money they will earn, if they sell more than 10 books, is m = 2b + 4.
In Step 1, Mike correctly determines the number of books sold by Sally as 11, so there is no error in this step.
In Step 2, Mike correctly substitutes the value of books sold by Sally (11) into the equation to find the money she will earn as 2(11) + 4 = 26. There is no error in this step.
In Step 3, Mike correctly determines the number of books sold by himself as 22, so there is no error in this step.
In Step 4, Mike incorrectly substitutes the value of books sold by himself (22) into the equation. Instead of using the equation as written, he mistakenly adds 4 to 22 first and then multiplies the result by 2. The correct equation should be m = 2(22) + 4 = 48.
Therefore, the error is made in Step 4.
The correct answer is D. Step 4.