3rd Grade - Math

LESSON PROBLEM: Estimation: You purchased 5 rice cookies and 4 rice candies with your weekly allowance. You ate three things. How many are left?


STUDY GUIDE

You know how to add and subtract numbers up to 10. But, in daily life you often need to know when a problem needs to be added or subtracted.

For example, you have 7 rice cookies. Your sister gives you 3. You want to know the number of cookies that you have. How can you figure this out? Would you add 7 and 3? Or would you subtract 3 from 7?

First find out if the first number will go up or go down. Are you putting something more to what you already have? Or, are you taking something away? You have 7 rice cookies of your own. Then your sister gives you three more.

Cookies you already have: OOOOOOO
Cookies your sister gives: OOO
Cookies you now have: OOOOOOO OOO

You now have more cookies than you had before. So you add the two numbers. When you put together two or more things, such as money or any other item, you add. The new number is bigger than the first number.

To find the number of rice cookies, add 7 and 3.

7 + 3 = 10

If your sister had 9 rice cookies and she gave you 3, then the number of rice cookies she has left is smaller than what she had at first. She has less rice cookies now. She has taken away 3 from the 9 that she had. Subtract 3 from 9 to find the number of rice cookies she has left. The number of rice cookies your sister had:

1 2 3 4 5 6 7 8 9

Number of rice cookies your sister gave you:

1 2 3 4 5 6 1 2 3

Number of rice cookies she has left:

1 2 3 4 5 6

Your sister has given or taken away 3 rice cookies. So she has fewer rice cookies now. We need to subtract. We write: 9 - 3 = 6

Now answer the following:

You placed 12 glasses of rice milk on the table. Your friends drank 5. How do you find the number of glasses that still have milk in them?
You have invited 11 friends to your birthday party. You have 5 rice drinks and 3 cans of rice milk. How do you find whether you have enough for all of the guests?
You invited 5 friends to a picnic. Your sister called 3 friends, as well. If you want to find out how much of each item to order - rice cookies, rice soup, rice noodles, how do you do it?
You put 12 bowls of rice pudding in the refrigerator in the morning. In the evening, there are 5 bowls of rice pudding left. How do you find the number of rice puddings that are missing?





ACTIVITIES

Your family is having a party. You have been given 5 boxes of rice cookies. Each box contains 12 cookies. You have been asked to place 5 cookies on each plate. Before taking the cookies from the box, try to find out how many would be left after you take 5 from the box.

Then take 5 more cookies from the box and place them on a plate.

Now count the cookies left in the box.

Compare what you counted with your work on paper.

When there are less than 5 cookies in the box, how many will you need to take from the next box.

Write the problem and compare your answer with the number of cookies you have taken from the other box.





EXTENDED LEARNING

You get a weekly allowance of $5. This is how you used your money:

Week 1: You get $5 and spend $3 on rice pudding and rice milk.

Week 2: You get $5 and spend $4 on rice cookies and rice candies.

Week 3: You get $5 and spend $5 on rice noodles and rice soup

Week 4: You get $5 and spend $2 on rice cake.

If you are asked to find whether you have saved money or you have overspent from your allowance, how would you do it?




VOCABULARY

  • situation
  • requires
  • original
  • resulting
  • combine
  • joining
  • fewer



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