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Home > CC2 > Chapter 1 > Lesson 1.1.2 > Problem 1-15


Maria was playing a game with her brother. She said, “I’m thinking of a number. When you multiply my number by six and add seven, you get twenty-five. What is my number?”

  1. Find Maria’s number.

    How big do you expect her number to be? Can you think of a reasonable number to try?

    Pick a reasonable number and try Maria's steps. Let's try . If Maria multiplies this number () by , she would get . Then, adding , she would get .

    Can you think of a number that might work better? Try it!

    Since is smaller than , let's choose a bigger number. Let's try . If Maria multiplies by , she would get . Adding , she would get . Since Maria gets by using this number, is the number she described.

    We now know that Maria's number is .

  2. Explain how you figured out your answer to Maria’s number puzzle.

    Can you describe with words the steps that you took to find Maria's number?