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Lesson 4 — Activity 1: Rounding Decimal Numbers
Completion requirements
Lesson 4 — Activity 1:
Rounding
Decimal Numbers
Getting Ready:
You looked briefly at decimal numbers when you were completing work on scientific notation. Let’s now look more closely at decimal numbers.
Here’s the place values for this decimal number:
Try This:
Identify the place value of the underlined digit in the following numbers:

3,456.578
 775,525.027
 32,194.647
 3,456.578: 5 is in the
tenths
place

775,525.027: 7 is in the
thousandths
place

32,194.647: 4 is in the
hundredths
place
Rounding decimal numbers is a good strategy to use when estimating amounts, such as the cost of items in a store.
Let’s first practise rounding decimal numbers to the nearest whole number:
If you saw an item in a store marked $8.56, you could do the following:
When rounding to the nearest whole number, begin by looking at the tenths place in the decimal number:

In the number 8.56, underline the number in the tenths place (the number 5 is in the tenths place).

If the underlined number is 4 or less, leave the number as it is; if the underlined number is 5 or greater, round up to the next whole number.

In this example, the underlined number is 5, so you would round up to the next whole number, which is 9.

$8.56 becomes $9.00 when rounded.
Now Try This:
Say you were looking at another item in a store and it was marked at $16.30.
Do the following:

Underline the number in the tenths place.

If the underlined number is 4 or less, leave the number as it is; if the underlined number is 5 or greater, round up to the next whole number.

What is $16.30 rounded to the nearest whole number?

Underline the number in the tenths place.

If the underlined number is 4 or less, leave the number as it is; if the underlined number is 5 or greater, round up to the next whole number.
 What is $16.30 rounded to the nearest whole number?
 You should have underlined the 3 as it is in the tenths place.
 Since the 3, is 4 or less, you would leave the number as it is.
 $16.30 rounded to the nearest whole number is $16.00.
Let's look now at further rounding of decimal numbers. First to the nearest tenths, then to the nearest hundredths.
Let's look now at further rounding of decimal numbers. First to the nearest tenths, then to the nearest hundredths.
Rounding to the Nearest Tenths
Michael
works at a stockyard. His job is to weigh each of the calves as they
are brought in. He must record the mass of each calf to the nearest
tenths of a kilogram.

Rounding to the Nearest HundredthsIn downhill skiing competitions, times are often only hundredths of a second apart.
