# Lesson 19 Situations and Equations

Let’s represent and solve problems.

## Warm-up Notice and Wonder: The Unknown

What do you notice? What do you wonder?

## Activity 1 Mai’s Beads

## Problem 1

Match each diagram with a situation. Explain your reasoning.

1:

2:

3:

Mai had 104 beads. She bought two packs of beads and now she has 124 beads. How many beads were in each pack?

Mai had some beads. She bought 2 more packs of beads and each pack has 10 beads in it. Now she has 124 beads. How many beads did Mai have before?

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?

## Problem 2

Match each equation with a letter for the unknown quantity to a situation in Problem 1.

## Activity 2 Represent, Solve, Explain

Kiran is setting up a game of mancala. He has a jar of 104 stones.

From the jar, he takes 3 stones for each of the 6 pits on his side of the board.

How many stones are in the jar now?

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

Solve the problem. Explain or show your reasoning.

Explain how you know your answer makes sense.

## Practice Problem

## Problem 1

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?

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

Solve the problem. Explain or show your reasoning.