SPACE ACADEMY · TRY, THINK, PLAY

Class 2: Number detectives

Translate representations, use place value and solve constrained number clues.

Try a quick challenge

Just a quick try. Not saved; no game rewards.

ExplorePlace value

Each flat is 100, each rod is 10, and each cube is 1. What number do the blocks show?

Base-Ten BlocksHundreds (100)Tens (10)Ones (1)
  1. 363
  2. 633
  3. 436
  4. 336
Need a hint?

Count the hundreds, tens, and ones separately, then combine their place values.

Answer & method
Answer D: 336

First find each group's value: 3 hundreds = 300, 3 tens = 30, and 6 ones = 6. Adding 300 + 30 + 6 = 336 in all.

Try more in game

ReasonPlace value

Which base-ten block picture shows 124?

  1. Picture A
  2. Picture B
  3. Picture C
  4. Picture D
Need a hint?

Match the hundreds digit to flats, the tens digit to rods, and the ones digit to small cubes.

Answer & method
Answer A: Picture A

Break 124 into place values: 1 hundred-flat (100), 2 ten-rods (20), and 4 unit cubes (4).

Try more in game

StretchPlace value

Find the 3-digit number. The hundreds, tens, ones digits add to 17. The tens digit is 3 more than the hundreds digit. The hundreds digit is 1 more than the ones digit.

?H?T?OThe hundreds, tens, ones digits add to 17.The tens digit is 3 more than the hundredsdigit.The hundreds digit is 1 more than the onesdigit.
  1. 362
  2. 153
  3. 584
  4. 953
Need a hint?

Use the digit differences together with the digit sum, then check every condition.

Answer & method
Answer C: 584

Make all three unknown digits equal to the hundreds digit: 17 − 3 + 1 = 15. Dividing by 3 gives 5; the tens digit is 8 and the ones digit is 4. The result is 584. Substitution checks every clue.

Try more in game
For grown-ups

Ideas to practise

  • Place value. A digit has a different value in each position. Count the places from the right.
  • Comparing quantities. Compare the values, not the size or spacing of their pictures.
  • Building numbers. Combine the place-value parts, including any zero places.

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 Instrument bay in Outer Planet Voyager. 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.

Choose a level

Explore

Foundations: read a representation and practise the underlying idea.

  • Read an original abacus
  • Count the numbers in a cloud that follow a digit rule
  • Compare place values and face values of digits
  • Read base-ten hundreds, tens and ones blocks
  • Read a number on a scaled number line
  • Match expanded form and place value in stories
  • Order four 3-digit numbers on beacons
Play Explore

Reason

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

  • Move a bead between place-value rods
  • Compare number expressions
  • Count the numbers in a cloud that follow a digit rule
  • Compare place values and face values of digits
  • Order four 3-digit numbers on beacons
  • Pick the block model that matches a 3-digit number
  • Put the right sign between two place or face values
Play Reason

Stretch

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

  • Solve linked digit clues
  • Combine two abacus numbers
  • Count the numbers in a cloud that follow a digit rule
  • Compare place values and face values of digits
  • Order four 3-digit numbers on beacons
  • Put the right sign between two place or face values
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 2 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.

Content and coverage notes. To report a confusing question, describe the grade, chapter, level and question on the contact page. Do not send children’s personal information.

Private, local saves

Game progress stays only in this browser, in three anonymous explorer slots. Clearing site data or closing a private session may remove it. Download a private backup from Help & saves; there is no cloud sync. The game checks saves before play and stops on save failures rather than pretending progress was saved.

These page examples never change a saved game. Game links carry question settings, not a learner’s answers. There are no names, school details, public profiles, chat, analytics or advertising SDKs in the game. Grown-up guidance · Privacy

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