SPACE ACADEMY · TRY, THINK, PLAY

Class 5: Decimal discoveries

Connect hundredths models to decimal quantities and check multi-part statements.

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ExploreComparing quantities

P: 26 x 4 = 104. Q: 7,882 > 7,304. R: XXXIX = 41. Which statements are NOT correct?

  1. All of P, Q and R
  2. P only
  3. R only
  4. P and Q
Need a hint?

Test each statement on its own, working out the true value, before choosing the option.

Answer & method
Answer C: R only

P is correct; Q is correct; R is not correct. So the answer is: R only.

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ReasonComparing quantities

Statement I: 1928 is divisible by 3. Statement II: The LCM of 4 and 10 is 40. Which option is correct?

  1. Both Statements are true
  2. Only Statement I is true
  3. Only Statement II is true
  4. Neither Statement is true
Need a hint?

Work out each statement on its own, then match the two results to an option.

Answer & method
Answer D: Neither Statement is true

Statement I is false: 1928 / 3 leaves remainder 2. Statement II is false: the LCM of 4 and 10 is 20.

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StretchComparing quantities

P: The 3 in 35,053 is worth 30,000. Q: 5,179 rounds to 5,000 (nearest 1000). R: 91 is a prime number. Which statements are NOT correct?

  1. R only
  2. Q only
  3. Q and R
  4. P and R
Need a hint?

Test each statement on its own, working out the true value, before choosing the option.

Answer & method
Answer A: R only

P is correct; Q is correct; R is not correct. So the answer is: R only.

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For grown-ups

Ideas to practise

  • Decimals and place value. Line up decimal places. One hundredth is one of 100 equal parts.
  • Comparing quantities. Compare the values, not the size or spacing of their pictures.

A game mission has 8 untimed questions. Only the game saves choices and hints. A finished mission earns one launch charge and participation towards the Science pod in Galaxy Command. The chapter goal is 8 different questions in finished sets; hints and wrong answers count as participation, not mastery. Some craft systems link more than one chapter.

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Explore

Foundations: read a representation and practise the underlying idea.

  • Read a hundredths grid as a decimal
  • Locate decimals on a number line
  • Use place value in a decimal chart
  • Add and subtract decimal money or measures
  • Convert between a decimal and a fraction
  • Judge three statements about numbers
Play Explore

Reason

Paper-style reasoning: connect clues, interpret a diagram or work backwards.

  • Read a hundredths grid as a decimal
  • Use place value in a decimal chart
  • Compare and order decimal cards
  • Add and subtract decimal money or measures
  • Convert between a decimal and a fraction
  • Judge three statements about numbers
  • Judge Statement I and Statement II
Play Reason

Stretch

Higher-order practice: link conditions, test statements and avoid a tempting wrong method.

  • Compare and order decimal cards
  • Locate decimals on a number line
  • Use place value in a decimal chart
  • Add and subtract decimal money or measures
  • Convert between a decimal and a fraction
  • Judge three statements about numbers
  • Judge Statement I and Statement II
Play Stretch

Levels change representations, clues and conditions, not just the numbers. These are practice formats, not validated exam-equivalent difficulty.

Using the feedback

Learning reports distinguish hinted answers from independent first choices. They consider up to 20 recent different, unhinted questions per skill and level, and wait for at least five before suggesting extra practice. Repeating the same question does not add evidence. Reports are practice evidence, not IQ scores, diagnoses, ranks or predictions of competition results.

Ask the learner to explain a drawing or check with objects too. Choose Explore or an earlier chapter when a step feels too large.

Sources & limits

The grade topics use SOF IMO Class 5 published topic syllabus as their primary reference. The SOF sample and CREST previous-year paper below informed representations and reasoning demands. Providers have different topic boundaries; their syllabi are not interchangeable.

Questions, diagrams, picture choices, hints and explanations are original Otterly work, not copied paper questions or publisher artwork. No Olympiad provider is affiliated with or endorses Space Academy. This is not complete exam preparation; follow classroom teaching and check the current official syllabus too. Independent educator review is still needed for difficulty and breadth.

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Original Otterly practice, not an official exam. Game progress stays on this browser.