Unit 2 · Topic 09 · Number Play
Ms. Rao mixed together every Number Play idea from the whole chapter into one revision sheet: patterns, primes, palindromes, digit sums, and supercells, all shuffled up.
Kabir panicked at first, thinking he needed a whole new set of rules to solve it.
Then he realised: it wasn't new maths at all — it was every idea he already knew, just recognising which tool fit which question.
"A good revision sheet doesn't teach anything new," said Ms. Rao. "It just mixes up everything you've learned, so you practise deciding WHICH tool to reach for." She handed out a sheet with five very different-looking questions.
Question 1 asked for the digit sum of 47,382. Kabir added the digits directly: 4+7+3+8+2=24. Question 2 asked whether 131 was a palindrome. Anaya read it backwards — 131 — same forwards and backwards, so yes. Question 3 asked for the supercells in the row 6, 2, 9, 4, 7. Working neighbor by neighbor, she found 6, 9, and 7 all beat their immediate neighbors.
Question 4 gave the start of a Collatz sequence, 5, and asked for the next three steps: 5 is odd (3x5+1=16), 16 is even (16/2=8), 8 is even (8/2=4) — so 16, 8, 4. Question 5 asked for the Kaprekar result of repeatedly applying the 4-digit Kaprekar process to 3524 — Kabir already knew it would eventually settle at 6174, the Kaprekar constant, no matter the starting digits (as long as they aren't all identical).
"See?" said Ms. Rao. "None of these needed a brand-new idea. Digit sum, palindrome-checking, supercells, the Collatz rule, and the Kaprekar constant — you'd met every single one already. The only new skill here is reading a question carefully enough to recognise which one it's actually asking for." Anaya nodded: "Revision isn't re-learning. It's practising recognition."
A revision sheet combines previously-learned ideas rather than introducing new rules — success depends on recognising which tool a question needs.
Digit sum: add up all the digits of a number.
Palindrome check: compare a number read forwards to the same number read backwards.
Supercell check: compare each cell only to its immediate neighbor(s), not the whole row.
Collatz rule: halve even numbers, triple-and-add-1 odd numbers, and repeat.
Find the digit sum of 58,206 and check if any rearrangement of its digits forms a palindrome.
Pick a 4-digit number with not-all-identical digits and apply the Kaprekar process until you reach 6174.
Loading questions…