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Finding Common Ground

A factor tree, and where it ends

One student splits 60 as 6 × 10. Another splits it as 4 × 15.

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Figure 1 — two routes down from 60, one set of ends.

Split any way. The ends do not change.

A factor tree splits a number until every branch is prime. Try 6 × 10 and 4 × 15. Both trees end on 2, 2, 3 and 5. The ends are the primes at the bottom of each tree. The primes may appear in a different order on the page.

Do not split with 1. A split like 1 × 60 does not make the number smaller.

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This track

  1. 0 Start here
  2. 1 The primes inside a number
  3. 2 A factor tree, and where it ends
  4. 3 The biggest one they share
  5. 4 Reading it off the two prime lists
  6. 5 When two step counts meet
  7. 6 The same two lists, read the other way
  8. 7 Which one does the question want?
  9. 8 Check it before you hand it in
  10. 9 Co-prime numbers
  11. 10 One table for the HCF and the LCM
  12. 11 The HCF, the LCM and the product
  13. 12 Checkpoint
  14. 13 The big picture
  15. 14 Track quiz

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