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MathidiaMathematics Academy
Place value and rounding
Lesson 4 of 75
Challenge

Round whole numbers and decimals

Objective. Round to a stated place value and explain the decision digit.

  1. 1. Learn
  2. 2. Worked example
  3. 3. Practice
  4. 4. Feedback
  5. 5. Continue

Learn: the key idea

Rounding replaces a number with a simpler nearby value. Find the place you are rounding to, then look at the next digit to the right, the decision digit. If it is 5 or more, round up; if it is 4 or less, keep the digit. For example, 5.376 to one decimal place: the tenths digit is 3 and the decision digit is 7, so it rounds up to 5.4. 126 883 to the nearest hundred is 126 900.

Worked example

Round 5.376 to one decimal place, and round 126 883 to the nearest hundred.

5.376 … 126
Illustrated card showing 5.376 … 126
  1. 1For 5.376 the rounding digit is the tenths digit, 3; the decision digit is 7.
  2. 27 is 5 or more, so round up: 5.4.
  3. 3For 126 883 the hundreds digit is 8; the decision digit (tens) is 8.
  4. 48 is 5 or more, so round up to 126 900.

Answer: 5.4 and 126 900

Concept mastery

Based on your past attempts at this lesson — the question types to practise again come first.

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Practice

Practice happens on its own screen, one question at a time. Answers stay hidden until you submit yours, and you can stop and pick up at the same question later.

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Common mistake. A common mistake is looking at the wrong digit or rounding every digit in turn, for example 5.376 → 5.38 → 5.4. Only the single decision digit next to the rounding place matters.

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