Factors & Primes
Rectangle maker, prime hunt, LCM and HCF.
Learn with Kutty
Go one screen at a time. Press Next when you are ready. Tap 🔊 Read to me to listen.
Break a number into prime building blocks, then use them to find HCF and LCM.
Look: Keep splitting until every branch ends in a prime (circled). 60 = 2 × 2 × 3 × 5.
✏️ Your turn!
Type your answer and press Check. Kutty will tell you if it is right.
1Write 84 as primes.
2HCF of 24 and 36?
3LCM of 4 and 6?
! Careful!
✗Saying the HCF of 12 and 18 is 36.
✓HCF is small (here 6). LCM is big (36).
✗Stopping a factor tree at 4.
✓Keep going until every end is prime.
See the whole lesson on one page
Break a number into prime building blocks, then use them to find HCF and LCM.
HCF is the biggest number that divides both. LCM is the smallest number both go into. HCF uses the shared bricks. LCM uses all the bricks.
Think of it like thisEvery number is built from prime bricks, like LEGO. 60 is built from 2, 2, 3 and 5.
- HCF
- Highest common factor.
- LCM
- Lowest common multiple.
Solved together
One bell rings every 12 minutes, another every 18. They ring together at 9:00. When do they ring together next?
Break both into primes.
12 = 2 × 2 × 318 = 2 × 3 × 3Put shared bricks in the middle.
LCM: multiply every brick in the picture.
2 × 2 × 3 × 3 = 36They ring together every 36 minutes.
9:00 + 36 min = 9:36
AnswerAt 9:36.
Now practise it
Kanakku makes new questions on factors & primes every time. It shows the working and gives a hint when you are stuck.