Whole Number Division

Carlos’s Method

Work Time

Carlos’s Method

Carlos wants to find 3 ÷ 23. He decides to use the same method he used to find 89 ÷ 4 in the previous lesson: multiply by the reciprocal.

At first, Carlos isn’t sure what to do with 23. What is the reciprocal of 23? He thinks back to a rule he learned: the multiplicative inverse, or reciprocal, of ab is ba. For example, the reciprocal of 4 is 14; the reciprocal of 15 is 5. So, Carlos determines that the reciprocal of 23 is 32. He then solves the problem as follows: 3 ÷ 23 = 3 • 32 = 92.

Thus, 3 ÷ 23 = 92.

  • Use Carlos’s method to find 6 ÷ 25.
  • Describe and explain each step of your solution.

Ask yourself:

Will the answer be greater than or less than 3? How can you use the reciprocal of 25 to solve the problem?