We included **HMH Into Math Grade 3 Answer Key**** PDF** **Module 9 Lesson 4 Use Mental Math to Assess Reasonableness** to make students experts in learning maths.

## HMH Into Math Grade 3 Module 9 Lesson 4 Answer Key Use Mental Math to Assess Reasonableness

I Can use mental math to determine the reasonableness of statements and answers.

**Spark Your Learning**

A store has 212 shirts for sale. The store sells 77 shirts. Luke says that there are about 130 shirts left to sell. Micah says that there are about 300 shirts left to sell. Whose statement is reasonable? Explain your thinking.

Answer:

Luke statement is reasonable than Micah.

Explanation:

A store has 212 shirts for sale.

Store sells 77 shirts.

The difference between these two is 212 – 77 = 135 and Luke said there are about 130 shirts to sell.

Micah said that there are about 300 shirts left to sell. Hence Luke’s statement is reasonble than Micah.

**Turn and Talk** For the statement that is not reasonable, what scenario would make the statement reasonable?

**Build Understanding**

1. A market has 53 cans of fruit and 44 cans of vegetables for sale. Rachel says that there are about 140 cans of food for sale. Is Rachel’s statement reasonable?

Answer:

Rachel’s statement is not reasonable.

Explanation:

In a market sale has 53 cans of fruit and 44 cans of vegetables.

And rachel says there are about 140 cans of food for sale.

In market a total of 97 cans of food are there but rachel said there are 140 cans of food. Therefore rachel’s statement is wrong.

A. How can you use a number line to show your thinking?

Answer:

B. How does your thinking compare to Rachel’s statement?

Answer:

The market has a total of 97 cans of food and rachel said there are about 140 cans of food for sale. By comparing both rachel said more number of can food than in the market.

C. Is Rachel’s statement reasonable? How do you know?

Answer:

No it is not reasonable.

Explanation:

As we are told rachel said more number of can food than in the market. Hence the given statement is wrong.

Think: When you decide if an answer is reasonable, the quantities and the operations have to make sense.

**Turn and Talk** How many fruit cans and vegetable cans could there be in order for Rachel’s statement to be reasonable?

Answer:

70 cans of fruit and 70 cans of vegetables.

Explanation:

There should be 70 cans of fruit and 70 cans of vegetables could there be in order for Rachel’s statement to be reasonable.

**Step It Out**

2. A toy store has 283 toys for sale. There are 69 board games. Hector says there are about 215 toys that are not board games. Is Hector’s statement reasonable? Use mental math to decide.

A. About how many toys are for sale?

- Make 283 a friendly number. 283 – __ = ___

Answer:

283 – 215 = 69.

Explanation:

The number of toys are for sale is 280 and it is a friendly number.

B. About how many board games are there?

- Make 69 a friendly number. 69 + ___ = ___

Answer:

69 + 1 = 70

Explanation:

There are 70 board games in the toy store.

C. Using friendly numbers, what equation can you write to solve the problem?

_______________

Answer:

215 + 69 = 283

Explanation:

The equation we can write to solve the problem is 215 + 69 = 283.

D. About how many toys are not board games? about ___ toys

Answer:

215 toys.

Explanation:

There are about 215 toys that are not board games and there are 69 board games.

E. Is Hector’s statement reasonable? Explain.

_______________

Answer:

Yes the Hector’s statment is reasonable.

Explanation:

A toy store has 283 toys for sale and 69 board games.

Hector says there are about 215 toys that are not board games.

By doing the difference 283 – 69 = 215.

**Check Understanding Math Board**

Question 1.

Mrs. Bice spends $93 on groceries and $47 on the heating bill. She says that she spends about $100. Is Mrs. Bice’s statement reasonable? Show your thinking.

Answer:

Mrs. Bice’s statement is not reasonable.

Explanation:

Mrs. Bice spends $93 on groceries and $47 on the heating bill.

Mrs. Bice said she spent about $100.

The total sum of groceries is $110.

By comparing both we can know that she spent more than $100. Hence the given statement is not reasonable.

**On Your Own**

**Show your thinking.**

Question 2.

**STEM** Cellular phone memory, which is stored on a Secure Digital card, or SD card, is measured in units of information called gigabytes or GB. The SD card in Ms. Patel’s phone has 128 GB. If she buys a new phone with 256 GB, she says she will have about 25 GB more. Is this reasonable? Explain.

Answer:

The statement Ms. patel’s said is not reasonable.

Explanation:

Ms. Patel’s phone has 128 GB and she bought a new phone with 256 GB. She also said that she have 25 GB more. So by doing the difference 256 – 128 GB the answer we get is 128 GB. Hence the given statment is wrong.

Question 3.

**Critique Reasoning** David has $50 in his pocket. He spends $23 on meat and $18 on fruits and vegetables at the market. He says he has about $40 left in his pocket. Is David’s statement reasonable? Explain.

Answer:

Question 4.

**Critique Reasoning** Ina says 185 – 79 is about 105. Is Ina’s statement reasonable? Explain your thinking.

Answer:

Ina’s statement is not reasonable.

Explanation:

Ina said 185 – 79 is 105 but if we subtract the answer we get is 106. Hence the Ina’s statement is not reasonable.

**I’m in a Learning Mindset!**

How did I support my partner when we were comparing strategies for checking if a statement was reasonable?

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