Grade by Grade
B. Number · Number Sense: Big Numbers, Square Roots and Rational Numbers

Rounding Decimals in Real Life

B1.6About 40 minutes
Learning goals
  • I can round decimal numbers to the nearest whole number, tenth or hundredth.
  • I can round negative decimals.
  • I can choose a sensible place to round to in a real situation.
  • I can tell when a real situation needs rounding up instead of rounding to the nearest.

Words to know

round
Replace a number with a nearby, simpler number.
rounding place
The place you are rounding to (whole number, tenth or hundredth).
precision
How exact a number is. 2.37 m is more precise than 2.4 m.
terminating decimal
A decimal that ends, like 0.375.
repeating decimal
A decimal with a pattern that goes on forever, like 0.333….

Remember from Grade 6

In Grade 6 you rounded decimals to the nearest whole number, tenth or hundredth, and rounded repeating decimals like 3.333… to $3.33. This year you will also round negative decimals and decide how much to round in different situations.

How to round (a quick review)

  1. Find the rounding place.
  2. Look only at the digit just to its right.
  3. If that digit is 5 or more, round up (add 1 to the rounding place). If it is less than 5, keep the rounding place the same.
  4. Drop the digits after the rounding place.
2.32.352.4
2.37 is closer to 2.4 than to 2.3, so 2.37 rounds to 2.4 (nearest tenth).
Worked example

Example 1: Three ways to round

Round 14.682 to the nearest whole number, tenth and hundredth.

  1. Whole number: look at the tenths digit, 6. Round up: 15.
  2. Tenth: look at the hundredths digit, 8. Round up: 14.7.
  3. Hundredth: look at the thousandths digit, 2. Keep: 14.68.

15, 14.7 and 14.68

Worked example

Example 2: Rounding money

A pack of 3 maple candies costs $4.99. What is the price of one candy?

  1. 4.99 ÷ 3 = 1.6633… (the 3s repeat).
  2. Money is rounded to the nearest cent, which is the nearest hundredth of a dollar.
  3. Look at the thousandths digit: 3. Keep: $1.66.

About $1.66 per candy.

Rounding negative decimals

Use the number line: round to whichever number is closer.

−3.47 is between −3.5 and −3.4. It is 0.03 away from −3.5 and 0.07 away from −3.4, so it rounds to −3.5.

A shortcut that works: round the number without its sign (3.47 → 3.5), then put the negative sign back (−3.5).

-3.5-3.45-3.4
−3.47 is closer to −3.5 than to −3.4.
Worked example

Example 3: Keep the zeros

Round 5.997 to the nearest hundredth.

  1. The hundredths digit is 9. The thousandths digit is 7, so round up.
  2. 9 hundredths + 1 hundredth = 10 hundredths. Regroup: 5.99 + 0.01 = 6.00.

6.00. Keep the zeros: they show the answer is precise to the hundredth. (6.00 m tells a builder more than 6 m.)

SituationUsually rounded toExample
Moneynearest hundredth (cent)$1.6633… → $1.66
A person's height in metresnearest hundredth (centimetre)1.534 m → 1.53 m
Temperature in a weather reportnearest tenth or whole degree−7.46°C → −7.5°C
Distance of a long trip in kmnearest whole number or tenth348.72 km → 349 km
The best rounding place depends on what you need the number for.

Sometimes you must round up

Rounding to the nearest isn't always right in real life. If paint for a room needs 2.1 cans, buying 2 cans isn't enough. You must buy 3. Always ask: "Does this answer make sense here?"

Hands-on activity

Unit price detectives

You need: a grocery receipt or flyer, a calculator, paper and a pencil.

  1. Find 4 items sold in packs, like 6 yogurts for $4.79 or 12 granola bars for $5.49.
  2. Use the calculator to find the price of one item. Many answers will have lots of decimal places.
  3. Round each to the nearest cent (hundredth). Which item costs the most per piece?
  4. Bonus: Measure the heights of family members in centimetres. Write each in metres (like 153.4 cm = 1.534 m), then round to the nearest hundredth of a metre and the nearest tenth.

Example: 6 yogurts for $4.79: 4.79 ÷ 6 = 0.79833… → $0.80 each.

Just for fun

Why should you never argue with a decimal?

It always has a point.

Your turn

1

Round 6.47 to the nearest tenth.

2

Round 12.384 to the nearest hundredth.

3

Round 0.96 to the nearest whole number.

4

Round 7.995 to the nearest hundredth.

5

Round −2.83 to the nearest tenth.

6

Three friends share $10 equally. How much does each get, rounded to the nearest cent?

7

Round 18.46°C to the nearest tenth.

More practice: warm-up

1

Round 3.2 to the nearest whole number.

2

Round 4.86 to the nearest tenth.

3

Round 0.349 to the nearest hundredth.

4

Round 9.5 to the nearest whole number.

5

Round 1.04 to the nearest tenth.

More practice: on your own

1

Write 2/3 as a decimal rounded to the nearest hundredth.

2

Round −0.558 to the nearest hundredth.

3

Seven friends share a $50 bill equally. How much should each pay? Is there a problem with rounding?

4

A scale shows 1.276 kg of cheese. Round it to the nearest tenth and to the nearest hundredth of a kilogram.

5

A half marathon is 21.0975 km. Round it to the nearest whole number, tenth and hundredth.

Challenge

1

A number with two decimal places rounds to 4.6 (nearest tenth). What are the smallest and largest numbers it could be?

2

Mia rounds 3.449 to the nearest tenth. She first rounds to the hundredth (3.45), then rounds 3.45 to the tenth (3.5). What went wrong?

3

One can of paint covers 10 m². The walls of a room have an area of 34.2 m². How many cans should you buy?

Check your understanding

Quiz

1.

Round 8.352 to the nearest tenth.

2.

Round 0.0742 to the nearest hundredth.

3.

Round −5.68 to the nearest tenth.

4.

Amounts of money in dollars are usually rounded to the nearest...

5.

Round 9.97 to the nearest tenth.

6.

You need 2.1 cans of paint and can only buy whole cans. How many should you buy?

For parents and teachers

Big idea: Grade 7 expectation B1.6 asks students to round decimal numbers to the nearest tenth, hundredth, or whole number, as applicable, in various contexts. Your child learned the rounding steps in Grade 6. In Grade 7 the focus is on contexts: which place makes sense, negative decimals, and when real life needs rounding up.

Common difficulties:

  • Looking at the wrong digit or rounding twice (3.449 → 3.45 → 3.5).
  • Regrouping 9s (7.995 → 8.00, not 7.100).
  • Dropping zeros that matter (6.00 vs. 6).
  • Rounding negative numbers the wrong way. Use the number line or round without the sign and put it back.

How to help: Do the unit price activity at the grocery store or with a flyer. Ask "How exact do we need to be here?" when you measure, shop or cook.