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Rounding and Estimating: Climb Rounding Ridge with Rory

Rounding and Estimating: Climb Rounding Ridge with Rory

Learn rounding and estimating: round any whole number, check calculations with quick estimates and round answers in real problems on a hilly number line.

  • Ages 9–11
  • About 45 min
  • Some thinking
  • Numbers
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What you'll learn

  • Round any whole number to the nearest 10, 100, 1,000 or million
  • Use the digit to the right of the rounding digit to decide
  • Why halfway numbers round up and why you never round in steps
  • Estimate by rounding to check whether an answer is sensible
  • Choose a sensible degree of accuracy and when to round up or down
  • Round decimals to one or two decimal places and money to the penny

Chapter by chapter

  1. Rounding to the nearest 10, 100 and 1,000 on a number line Free to try

    Year 6 maths · 1

  2. Rounding large numbers to the nearest 10,000, 100,000 and 1,000,000

    Year 6 maths · 1

  3. Using estimation to check answers to calculations

    Year 6 maths · 2

  4. Choosing an appropriate degree of accuracy in real-life problems

    Year 6 maths · 2

  5. Solving problems with answers rounded to a specified degree of accuracy

    Year 6 maths · 3

  6. Summit Challenge: rounding and estimating quiz (10 questions)

What the chapters cover in the national curriculum in England:

  1. Year 6 maths: Round any whole number to a required degree of accuracy
  2. Year 6 maths: Use estimation to check answers to calculations and determine, in the context of a problem, an appropriate degree of accuracy
  3. Year 6 maths: Solve problems which require answers to be rounded to specified degrees of accuracy

About this adventure

Rounding Ridge is an interactive rounding and estimating game that teaches children aged 9–11 to round any whole number, use estimation to check answers and round answers to the accuracy a problem needs. It follows the Year 6 maths curriculum in England.

With Rory the mountain goat as their guide, players drop number balls onto hills where the valleys are multiples and the hilltops are halfway points, so they can see which multiple each number is nearest to. On a place value chart they find the rounding digit and the digit to its right that decides. They also check a calculating robot's work with estimates and round decimals and money to the nearest penny.

The game looks out for common mistakes, such as rounding in steps or forgetting to carry when a 9 goes up. Optional warm-ups refresh place value and decimals, and a ten-question Summit Challenge brings everything together.

Questions and answers

How do you round a number, in simple words?

Find the digit in the place you are rounding to, then look at the digit just to its right. If that digit is 5 or more, the rounding digit goes up by one; if it is 4 or less, it stays the same. Every digit after it becomes zero.

Why does a number ending in 5 round up?

A number ending in 5 is exactly halfway between two multiples, so mathematicians agreed that halfway always rounds up. That way everyone gets the same answer: 345 rounded to the nearest 10 is 350, and 2,450 rounded to the nearest 100 is 2,500.

How does estimating help you check an answer?

An estimate is a quick answer worked out with rounded numbers, such as 300 × 20 = 6,000 for 298 × 21. If the real answer is nowhere near the estimate, for example about ten times too big, there is probably a mistake to look for.

What age is this rounding game for?

The game is designed for children aged 9 to 11 and matches the Year 6 maths curriculum in England. Confident Year 5 pupils can play too, and short warm-ups on place value and decimals help anyone who needs a refresher first.

What does the rounding game include and how long does it take?

It has five chapters, two optional warm-ups and a ten-question Summit Challenge quiz. Playing everything takes about 45 minutes, and children can choose any chapter from the map and return to it whenever they like.

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