Check it before you hand it in
Someone says HCF(12, 18) = 9. Is that right?
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Step 1 of 5
- Candidates: 9, 3, 6.
- Test 1: does it go into both? 9 fails.
- 3 and 6 both pass test 1.
- Test 2: does anything bigger go into both? 3 fails.
- 6 passes both. HCF(12, 18) = 6.
No. 9 does not go into 12.
Two tests for the HCF
Test 1: does it go into both numbers? Test 2: does anything bigger also go into both? Only 6 passes both.
3 goes into both. But 6 is bigger and also goes into both. So 3 fails Test 2.
Two tests for the LCM
Test 1: do both numbers go into it? Test 2: does anything smaller also pass Test 1? Only 36 passes both.
72 passes Test 1, but 36 is smaller. So 72 fails Test 2.