Section D: Practice Problems Solve Two-Step Problems

Section Summary


In this section, we used rounding to estimate answers to problems. This helped us decide if our answers to problems made sense based on the situation and the numbers in the situation.

We also wrote equations with an unknown and used diagrams to solve for the exact answer in problems.


Mai had 104 beads. She bought 2 more packs of beads and each pack has 10 beads in it. How many beads does she have now?


Equation with an unknown:

Problem 1 (Lesson 17)

There are 708 students at the school. Three hundred ninety-four students are in the cafeteria and the rest are in class. Han estimates that 400 students are in class. Do you agree with Han’s estimate? Explain or show your reasoning.

Problem 2 (Lesson 18)

Select all equations that match the tape diagram.

Diagram. One rectangle split into 6 parts. Total length, 110. 1 part, labeled question mark. Other 5 parts labeled 6.

Problem 3 (Lesson 19)

There are 240 connecting cubes in the box. Five students each take 9 connecting cubes from the box. How many connecting cubes are left in the box?

  1. Write an equation to represent the situation.  Use a letter for the unknown quantity.

  2. Solve the problem. Explain or show your reasoning.

Problem 4 (Lesson 20)

Andre has 245 cards. He bought 7 more packages of cards. How many cards does he have now?

  1. What information do you need to know to answer the question?

  2. Write an expression to represent the situation. Use a letter for the unknown quantity.

Problem 5 (Exploration)

For each equation, draw a diagram and write a situation with a question.

Problem 6 (Exploration)

  1. A question in a subtraction situation can be answered with an estimate of “about 200.” What could the subtraction situation be?

  2. A question in a situation that uses addition and multiplication could be answered with an estimate of “about 300.” What could the situation be?