Groups of students were first given 10 to 12 100's boards each. Each board was numbered and they were asked to cut out all the multiples of the number written on the board. For example, if the number was 4, then all the multiples of 4 were cut. There was one board in which all the numbers were coloured with a single colour.
When each board was overlapped with the coloured hundreds boards, all the numbers seen were the multiples a given number. the image above was taken when the board numbered 6 was placed on the hundreds board. All the numbers you can see are the multiples of 6. Similarly, the image below shows the multiples of 9. This helped the students to understand multiples.
Moreover, when you overlap the 100's board numbered 6 AND 9 on the coloured board, the numbers that you can see are COMMON MULTIPLES of 6 and 9: 18, 36, 54 and 72. Amongst these the least number is 18. Hence 18 is the LEAST COMMON MULTIPLE of 6 and 9.