Hcf....First we have to define the students concept of factor, for this write 4 on board and ask them to give two numbers, to multiply to get 4. They tell it will be 2×2. Now put some bigger numbers as 10, 20, 30 etc. By which they can understand the concept of factor. Now take 4 and 10 together and write their factors on board by asking them. Now ask them to track the common factor between these two, they say it will be 2. Now we can tell them by this we can get H.C.F. of two numbers. L.c.m.... Tell the students that multiple means table, now as full from of l.c.m. is lowest common multiple. Now tell the students to write table of 2and 10, one by one, it will be like this...... 2=2,4,6,8,10,12,14,16,18,20, 22,24,26,28,30,32,34 10=10,20,30,40 Now ask them what are common multiples in above two's, they will tell 10,20,30, put a circle around the numbers 10,20,30. Now ask the students which is the lowest number between 10,20,30. They tell 10. Here we get L.CM. or lowest common multiple of 2 and 10.

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