Rounding Numbers

What is "Rounding" ?

Rounding ways making a number simpler only keeping its value close to what it was.

The consequence is less accurate, but easier to utilise.

round 73 is 70, 76 is 80

Example: 73 rounded to the nearest ten is seventy, because 73 is closer to 70 than to 80. Only 76 goes up to 80.

Common Method

There are several different methods for rounding. Hither nosotros look at the common method, the one used by about people.

First some examples (explanations follow):

How to Round Numbers

  • Make up one's mind which is the concluding digit to keep
  • Leave it the same if the next digit is less than 5 (this is called rounding downward)
  • Only increase it by 1 if the adjacent digit is 5 or more (this is called rounding up)

Case: Round 74 to the nearest ten

  • Nosotros desire to proceed the "seven" (it is in the 10s position)
  • The adjacent digit is "four" which is less than 5, then no modify is needed to "vii"

Answer: lxx

(74 gets "rounded down")

Example: Round 86 to the nearest 10

  • We want to keep the "viii"
  • The side by side digit is "6" which is v or more than, so increment the "8" by ane to "ix"

Answer: 90

(86 gets "rounded upward")

So: when the offset digit removed is 5 or more, increase the concluding digit remaining past 1.

Why does 5 go up ?

5 is in the heart ... and then we could go upwards or downward. Simply we demand a method that everyone agrees to.

So think most sport: we should have the aforementioned number of players on each team, right?

soccer teams
  • 0,ane,two,3 and four are on team "down"
  • 5,6,seven,8 and 9 are on team "up"

And that is the "common" method of rounding. Read about other methods of rounding.

A farmer counted 87 cows in the field, but when he rounded them upwards he had ninety.

Rounding Decimals

Offset work out which number will be left when we finish.

  • Rounding to tenths means to leave ane number later on the decimal point.
  • Rounding to hundredths means to go out two numbers after the decimal indicate.
  • etc.

3.1416 rounded to hundredths is iii.xiv

every bit the next digit (one) is less than 5

3.1416 rounded to thousandths is 3.142

as the next digit (6) is more than than 5

1.2735 rounded to tenths is one.3

every bit the next digit (7) is 5 or more

To round to "so many decimal places" count that many digits from the decimal point:

1.2735 rounded to 3 decimal places is i.274

as the adjacent digit (5) is 5 or more

Rounding Whole Numbers

We may want to round to tens, hundreds, etc, In this example we replace the removed digits with naught.

134.9 rounded to tens is 130

as the next digit (four) is less than 5

12,690 rounded to thousands is 13,000

as the next digit (6) is 5 or more

fifteen.239 rounded to ones is 15

as the next digit (ii) is less than v

Rounding to Pregnant Digits

To round to "so many" significant digits, count digits from left to right, and then round off from there.

1.239 rounded to 3 significant digits is 1.24

as the adjacent digit (ix) is 5 or more than

134.9 rounded to one significant digit is 100

as the next digit (3) is less than five

When there are leading zeros (such every bit 0.006), don't count them because they are simply at that place to show how small the number is:

0.0165 rounded to 2 pregnant digits is 0.017

as the adjacent digit (5) is 5 or more than

significant digits

Pregnant Digit Computer

(Try increasing or decreasing the number of pregnant digits. Also try numbers with lots of zeros in front of them like 0.00314, 0.0000314 etc)