Lesson 8 of 15
Check it before you hand it in
Show on a big screenSomeone 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.
Try the lab to finish this lesson.