Page 14 - Math Smart - 7

CHAPTER 1.2

In this chapter
Lowest Common
Pupils should be able to:
• find the Lowest
Multiples and Highest
Common Multiple (LCM)
• find the Highest
Common Factor (NCR)
Common Factors
• use factor trees
Now that you have worked through factors and multiples, you will
know that a factor is a number that divides another number exactly,
with no remainder. In this chapter we are going to look at Lowest
^ RECALL Common Multiples (LCM) and Highest Common Factors (HCF).

List all the factors of
72 and 108. Then find We can use lowest common multiples to solve
the highest common problems that involve:
factor. • purchasing multiple items in order to have
enough. For example, putting together
List the multiples
some party bags. Balloons are sold in bags
of 12 and 16. Find
of 20 and candy bars are sold in bags of 8.
the lowest common
What is the minimum number of balloons
multiple.
and candy bars you need in order to have
Find the lowest an equal number of balloons and candy
common multiple of bars in each party bag?
5, 6 and 9. • figuring out when two things will happen
again at the same time. For example, two bells are set to ring at different
time intervals. One bell rings every 7 minutes, and the other bell rings every
8 minutes. Both bells have just rung. After how many minutes will both bells
ring at the same time again?

We can use highest common factors to solve problems that involve:
• arranging objects in rows or groups. For example, you have 12 movie DVDs,
24 wildlife DVDs, and 30 musical DVDs. You need to pack these DVDs into
containers. You can only pack one type of DVD in each container. Each
container must have the same number of DVDs. What is the greatest number
of DVDs you can pack in each container?
• splitting things into parts of equal size, so that the parts are as large as
possible. For example, you can use your knowledge of highest common
factors to help you solve an everyday problem. You have two pieces of cloth.
One piece is 32 cm wide and the other piece Is 48 cm wide. You want to cut
both pieces into equal widths that are as wide as possible. How wide should
you cut the pieces into?

UNIT1 Factors, Multiples and Primies