Printing: use your browser's print (Ctrl+P / ⌘P). It comes out as exactly 4 A4 sheets (2 pieces of paper double-sided). No answers in here.

time yourself

Maths A (new)Tue 8 September1 / 4

Using common multiples and common factors

Last week you learned the words. This week they become tools

Name Date

Try this first

List every factor of 12, and every factor of 18.
Then circle the numbers that appear in both lists.

1Factors of 12:

Factors of 18:

In both:

The largest circled number is the greatest common divisor.

Lowest common multiple → for adding fractions　/　Greatest common divisor → for cancellingThese two lines are the whole of this week

Now you

2Find both the greatest common divisor and the lowest common multiple of 8 and 12.

time yourself

Maths A (new)Tue 8 September2 / 4

Using common multiples and common factors

Name Date

3Find the greatest common divisor of 15 and 20.

4Find the lowest common multiple of 6 and 9. Explain in words how it differs from 6 x 9 ＝ 54.

5A sheet of paper is 18 cm by 24 cm. It is cut into identical squares with nothing left over. What is the largest possible side length, and how many squares are there?

What kind of number divides both 18 and 24 exactly?

6A red lamp flashes every 12 seconds and a blue lamp every 18 seconds. They have just flashed together. After how many seconds do they flash together again?

time yourself

Maths A (new)Tue 8 September3 / 4

Using common multiples and common factors

Name Date

7List every whole number from 1 to 50 that is a multiple of both 4 and 6.

8Two whole numbers have greatest common divisor 8 and lowest common multiple 48. What could the two numbers be?

The product of two numbers equals GCD x LCM.

Which tool is it

9Find both the greatest common divisor and the lowest common multiple of 16 and 24.

10Of the whole numbers 1 to 60, write every one that is a multiple of both 5 and 6.

time yourself

Maths A (new)Tue 8 September4 / 4

Using common multiples and common factors

Name Date

1136 pencils and 24 erasers are shared out equally with none left over. What is the largest number of people, and what does each get?

12Question 5 (cutting squares) and question 6 (flashing together) used different tools. Which used the greatest common divisor and which the lowest common multiple? Say why.

The important question today. Naming it matters more than doing it.

Extra · you may skip this

Find the lowest common multiple of 3, 4 and 6. Three numbers work the same way.