Lesson 20 How Much in the Group?

- Let’s solve more problems involving multiplication and division with fractions.

Warm-up Estimation Exploration: What Number Goes in the Blank?

What number goes in the blank?

Record an estimate that is:

too low	about right	too high

Activity 1 Different Equations

Problem 1

If $\frac{1}{3}$ of the class is 9 students, how many students are in the class?

Explain or show your reasoning.

Problem 2

Explain how each of these equations represents this situation.

$\frac{1}{3} \times$ $= 9$
$\div 3 = 9$
$3 \times 9 =$

Activity 2 How Big is the Class?

Jada’s class has 24 students in it. That is $\frac{1}{4}$ of the total students in the 5th grade. How many students are in the 5th grade? Explain or show your reasoning.
Select all the equations that represent this situation.
1. $\frac{1}{4} \times 24 =$
2. $\div 4 = 24$
3. $\frac{1}{4} \div 24 =$
4. $24 = \frac{1}{4} \times$

Activity 3 How Many in One Group?

Solve each problem. Show or explain your reasoning.

250 mg of calcium is $\frac{1}{4}$ of the daily recommended allowance. What is the daily recommended allowance of calcium? Show or explain your reasoning.
A rocket took 60 days to get $\frac{1}{5}$ of the way to Mars. How many days did it take the rocket to get to Mars? Show or explain your reasoning.

Practice Problems

Problem 1

3 ounces is $\frac{1}{4}$ of the package of sunflower seeds. How many ounces of sunflower seeds are in the whole package? Explain or show your reasoning.

Problem 2

A person drove 5 miles. That is $\frac{1}{3}$ of the distance from their home to work. How far is it from the person’s home to work? Explain or show your reasoning.