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⚖️ Topics & explainers · 4 min read

Comparing and ordering numbers: a Class 3 explainer

How Class 3 children compare and order numbers digit by digit, with worked examples and the greatest-number trap that appears in SOF IMO papers.

Comparing numbers is deciding which of two numbers is bigger — and doing it by looking at digits, not by guessing. It sounds simple, but olympiad papers dress it up: ordering a list, finding a number between two others, or building the greatest possible number from given digits.

The idea in one minute

  • A number with more digits is always bigger: any 3-digit number beats any 2-digit number.
  • If two numbers have the same count of digits, compare from the left — hundreds first, then tens, then ones.
  • Stop at the first place where the digits differ; that place decides the winner.
  • Ascending means smallest to largest; descending means largest to smallest.

✏️ Warm-up: pick the greatest

Which of these numbers is the greatest?

  1. A489
  2. B498
  3. C449
  4. D494
Show the answer

Answer: 498. All four numbers have 4 in the hundreds place, so move to the tens. 498 has 9 tens, 494 has 9 tens too — so compare their ones: 8 beats 4. 489 and 449 have only 8 and 4 tens. The greatest is 498.

✏️ Level up: a number in between

Which number lies between 340 and 350?

  1. A335
  2. B348
  3. C352
  4. D360
Show the answer

Answer: 348. A number between 340 and 350 must be bigger than 340 and smaller than 350. 335 is too small, while 352 and 360 are too big. Only 348 fits: 340 < 348 < 350.

✏️ Olympiad twist: build the greatest number

Using each of the digits 3, 9 and 0 exactly once, what is the greatest 3-digit number you can make?

  1. A930
  2. B903
  3. C939
  4. D390
Show the answer

Answer: 930. To build the greatest number, put the biggest digit in the biggest place: 9 in the hundreds, then 3, then 0 — giving 930. Note that 939 is a trap: it uses the digit 9 twice, which the question does not allow.

Comparing and ordering has its own set of levels inside LittleMathematicians’s Class 3 Number Sense topic, and the questions get twistier as your child’s mastery climbs — from picking the greatest to building numbers from digits. It is free during early access if you would like to try a level together.

Practice this the fun way

Adaptive levels, exam-pattern mocks and progress you can see — free during early access.

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Keep reading

Place value for Class 3: what each digit is really worthA plain-words explainer of place value for Class 3 — face value vs place value, worked examples, and the classic trap in SOF IMO questions.4 min read →Number Sense for the Math Olympiad (Classes 3–5)What Number Sense means in the SOF IMO for Classes 3–5: place value, comparing and ordering numbers, the classic traps, and worked examples.6 min read →Class 3 IMO preparation: syllabus, routine and what good looks likeA parent’s guide to preparing a Class 3 child for the SOF IMO: the syllabus topics that matter, a gentle routine, and realistic expectations.6 min read →