Rounding Decimal Numbers

1. Rounding Decimal Numbers Sometimes close enough is good enough!

2. Why do we need to know how to round decimals? Molly has $16 in her pocket • She buys: • 3 hotdogs @ $1.89 each • 3 milkshakes @ $2.19 each • 3 Large French fries @ $ $1.79 each Does she have enough money?

3. Gas costs $1.79 per gallon I’m running on empty and I have a 20 gallon tank on my truck…… About how much will it cost to fill up?

4. You have one hour to take a 50 question test. About how much time can you spend on each question? Close enough is good enough!

5. The Rounding Poem Find your number Look right next door 4 or less, just ignore 5 or more add one more!

6. Rounding Whole Numbers Round 474 to the closest hundred. 474 Find your number Look right next door Four or less, just ignore Five or more, add one more

7. 474 Rounded to the hundreds becomes 500 Round 474 to the closest 10’s 474 Just ignore - 470

8. Try These • 4,215 • 394 • 279 • 127,591 • 638

9. Are You Right? • 4,215 4,200 • 394 400 • 279 300 • 127,591 127,600 • 638 600

10. What about decimal numbers The same rules (and poem) apply! Round 4.167 to the closest hundredths 4.167 Find your number Look right next door 4.17

11. Remember If you are asked to round to the nearest tenth…….your answer stops at the tenth place! Example: Round 42.73 to the closest tenth would be 42.7

12. Special Case!Rounding a 9 Round 2.197 to the closes hundredths Since there is a “9” in the hundredths place consider the tenth and hundredths together – 19 – do you leave it at 19 or move it to 20?

13. Round 4.95 to the closest tenth Since there is a “9” in the tenth spot consider the ones and tenths together…… should you leave it at 49 or move it to 50? 4.95 rounded to the nearest tenth is 5.0

14. Try these Round to tenths: Round to hundredths 4.56 4.6 18.784 18.78 5.32 5.3 9.46 9.456 10.00 0.98 1.0 9.997