1. Birney Tech Academy, Mrs Oste
Rounding
Birney Tech Academy, Mrs Oste

2. Rounding is useful.
It helps you estimate sums by making numbers easier to work with.
Example:
Senecca picked 43 apples and Serenity picked 29 apples. About how many apples did they pick altogether?

3. Keyword
Senecca picked 43 apples and Serenity picked 29 apples. About how many apples did they pick altogether?
The word “about” tells me I can estimate. I don’t need the exact answer, just a close answer. Yay!
Look for other keywords like estimate.

4. Rounding to the Nearest Ten
Senecca picked 43 apples and Serenity picked 29 apples. About how many apples did they pick altogether?
Rounding to the Nearest Ten
Now I will round off the apples. Senecca has 43. The nearest tens are 40 or 50.
Hmmm… is 43 closer to 40 or 50?

5. Rounding Rules: There are two simple rules to follow.
If the value in the ones places is 1,2, 3, or 4 - Round down.
If the value in the ones place is 5, 6, 7, 8, or 9 - Round up.

6. Does 43 round down to 40 or up to 50?
If you answered round down to 40, you are correct. Senecca has about 40 apples.

7. Let’s not forget about Serenity!
Serenity picked 29 apples. Let’s remember the rounding rules.
If the value in the ones places is 1,2, 3, or 4 - Round down.
If the value in the ones place is 5, 6, 7, 8, or 9 - Round up.
Is 29 closer to 20 or 30?

8. Serenity has about 30 apples! Yay!
Now we have to add Senecca’s 40 apples and Serenity’s 30 apples.
All we have to do is add Can you do that?

9. The Solution
Senecca picked 43 apples and Serenity picked 29 apples. About how many apples did they pick altogether?
40+30= 70 apples
That’s a lot of apples!

10. Let’s talk about estimating the difference to a subtraction problem.
Chris went Pokemon hunting. He had 95 Ultra Balls. Chris found a Mew Two and used 38 Ultra Balls to catch it. About how many Ultra Balls does Chris have left?

11. Chris went Pokemon hunting. He had 95 Ultra Balls
Chris went Pokemon hunting. He had 95 Ultra Balls. Chris found a Mew Two and used 38 Ultra Balls to catch it. About how many Ultra Balls does Chris have left?
The word “about” tells me I need to give an estimate, not the real answer. So let’s round these numbers to make them easier to work with.

12. Chris went Pokemon hunting. He had 95 Ultra Balls
Chris went Pokemon hunting. He had 95 Ultra Balls. Chris found a Mew Two and used 38 Ultra Balls to catch it. About how many Ultra Balls does Chris have left?
95 rounds up to 100.
38 rounds up to 40.
= 60
Chris still has about 60 Ultra Balls left.