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 , 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 for the money earned, if they sell more than 10 books, is m = 2b + 4, where b represents the number of books sold, and m represents the money earned.
In step 1, Mike correctly determined that b=22, which represents the correct number of books he sold.
In step 2, Mike correctly substituted the value of b=22 into the equation, m = 2(22) + 4, which represents the correct calculation for the money he earned.
In step 3, Mike correctly determined that b=22, which represents the correct number of books he sold.
In step 4, Mike incorrectly calculated m = 2(22 + 4), which means he made an error.
Therefore, the answer is D. Step 4.