Lesson 1: Unit Pricing - Getting Into Its

   Getting Into It

Rounding

When performing calculations, especially when division is involved, you may end up with decimal values. To make these decimal values easier to work with, they can be rounded by replacing the number with an approximation involving fewer decimal places. There are various methods for rounding, and three common methods are described below.

Rounding
Replacing one value with another, simpler value that is approximately equal to the original.

Rounding to an Increment

"Round to the nearest integer" and "round to the nearest tenth" are both examples of rounding to an increment. To do this, find the digit of interest, and look to the digit on its right. If that value is less than 5, keep the digit of interest the same. If the value to the right is greater than or equal to 5, add one to the digit of interest. In either situation, remove any values to the right of the digit of interest.

Task 1


Round 4.37 to the nearest whole number.

Find the whole digit 4.37
Check the digit to the right 4. 37
The digit to the right is less than 5, so do not nchange the whole digit. Remove any digits after the whole digit. 4

Task 2


Round 12.357 to the nearest tenth.

Find the tenths digit 12. 357
Check the digit to the right 12.3 57
The digit to the right is 5, so add 1 to the tenths digit. Remove any digits after the tenths digit. 12.4

Rounding Up

Sometimes it makes sense to round a value up, regardless of what the digit is to the immediate right of the digit of interest.

Task 3


Adam needs 13 m2 of wall paper. How many 4 m2 rolls should he buy?

\(\frac{13\,\text{m²}}{4\,\text{m²}}=3.25\)

Although the tenths digit is a 2, you cannot round this value down to 3 rolls because 3 rolls will not be enough to finish the project. Adam will need to buy 4 rolls of wallpaper.


Rounding Down

Sometimes it makes sense to round a value down, regardless of what the digit is to the immediate right of the digit of interest.

Task 4


How many 15 cm strings can be cut from 100 cm?

\(\frac{100\,\text{cm}}{15\,\text{cm}}=6.\overline{6}\)

Although the tenths digit is a 6, you cannot round this value up to 7 because you are looking for the number of 15 cm strings. You can only cut 6 full length strings.


In this course, assume you will round to one decimal place, unless otherwise stated. The exception is money where you will round to 2 decimal places.


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