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🧮 Topics & explainers · 5 min read

Large numbers in Class 4: reading and building 5- and 6-digit numbers

How Class 4 children read, compare and build 5- and 6-digit numbers, with worked examples and the smallest-number trap from SOF IMO papers.

In Class 4, numbers grow from hundreds into ten thousands and lakhs — 5- and 6-digit numbers. Nothing new is invented: the same place-value idea from Class 3 simply gets more places. The challenge is keeping track of them, especially when a question asks a child to build a number from loose digits.

The idea in one minute

  • The places, from the right: ones, tens, hundreds, thousands, ten thousands, lakhs.
  • Commas in the Indian system group the digits for reading: 43,208 reads as forty-three thousand two hundred eight.
  • The successor of a number is one more; the predecessor is one less — watch for carrying across places, as in 79,999 + 1.
  • To build the smallest number from given digits, put the smallest digit first — unless it is 0, which can never lead.

✏️ Warm-up: place value in a big number

What is the place value of 3 in the number 43,208?

  1. A3
  2. B300
  3. C3,000
  4. D30,000
Show the answer

Answer: 3,000. Read 43,208 from the right: 8 ones, 0 tens, 2 hundreds, 3 thousands, 4 ten thousands. The 3 sits in the thousands place, so its place value is 3 × 1,000 = 3,000.

✏️ Level up: the successor of 79,999

What is the successor of 79,999?

  1. A79,998
  2. B80,000
  3. C79,000
  4. D80,999
Show the answer

Answer: 80,000. The successor means one more: 79,999 + 1. Adding 1 to the 9 in the ones place carries through every 9 — ones, tens, hundreds and thousands all roll over to 0, and the 7 in the ten-thousands place becomes 8. So the answer is 80,000. (79,998 is the predecessor, one less.)

✏️ Olympiad twist: smallest number from given digits

Using each of the digits 5, 0, 3, 8 and 1 exactly once, what is the smallest 5-digit number you can make?

  1. A01,358
  2. B10,358
  3. C10,385
  4. D13,058
Show the answer

Answer: 10,358. The smallest digit should lead — but a number cannot start with 0, or it stops being a 5-digit number. So start with the next smallest digit, 1, put the 0 right after it, then the rest in increasing order: 1, 0, 3, 5, 8 gives 10,358. The trap option 01,358 starts with 0, and 10,385 puts 8 before 5.

Large numbers are the backbone of LittleMathematicians’s Class 4 Number Sense levels: early ones practise reading and place value, later ones bring in successors, comparisons and digit-building puzzles as mastery rises. It is free during early access if your child would like to climb a few levels.

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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 →Roman numerals for Class 4: the seven letters and the subtraction ruleA Class 4 explainer of Roman numerals — the seven symbols, when to subtract, worked examples, and the illegal-numeral trap in SOF IMO papers.5 min read →Class 4 IMO preparation: the year fractions and geometry arriveHow to prepare a Class 4 child for the SOF IMO: large numbers, roman numerals, fractions and geometry — plus a routine that fits a nine-year-old.6 min read →