Transcript Rounding Decimal Numbers

Rounding Decimal Numbers
Sometimes close enough is good
enough!
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?
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?
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!
The rounding poem
Find your number
Look right next door
4 or less, just ignore
5 or more add one more!
Rounding Whole Numbers
Round 474 to the closest hundred.
474
1. Find your number
2. Look right next door
3. Four or less, just ignore
Five or more, add one more
474 rounded to the nearest hundreds is 500
Round 474 to the closest 10’s
474
Just ignore - 470
Try These
•4,215 (hundred)
•394 (ten)
•27 (ten)
•127,591(ten thousand)
•638 (hundred)
Rounding Decimals
The same rules (and poem) apply!
Ex: Round 4.167 to the closest hundredths
4.167 1. Find your number
2. Look right next door
4.17
Hint: When rounding decimals your answer STOPS in the
place you are rounding to. In this example we were asked
to round to the nearest hundredth so our answer stops in
the hundredths place.
Remember
If you are asked to round to
the nearest tenth…….your
answer
place!
stops at the tenth
Example: Round 42.73 to the
closest tenth would be 42.7
Special Case!
Rounding a 9
Round 2.197 to the nearest hundredths
Since there is a “9” in the hundredths
place and we have to round up, consider
the tenth and hundredths together – 19 –
do you leave it at 19 or move it to 20?
2.197 would become 2.20
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
Try these
Round to tenths:
Round to hundredths:
4.56 4.6
18.784
18.78
5.32 5.3
9.456
9.46
0.98 1.0
9.997
10.00