Exercise 1H 1
MR
Find the LCM of each pair of numbers.
a 4 and 5
b 7 and 8
c 2 and 3
d 4 and 7
e 2 and 5
f 3 and 5
g 3 and 8
h 5 and 6
2
What connection is there between the LCMs and the pairs of numbers in question 1?
3
Find the LCM of each pair of numbers.
a 4 and 8 EV
b 6 and 9
c 4 and 6
d 10 and 15
4
Does the connection you found in question 2 still work for the numbers in question 3? If not, explain why not.
5
Find the LCM of each pair of numbers.
6
a 24 and 56
b 21 and 35
c 12 and 28
d 28 and 42
e 12 and 32
f 18 and 27
g 15 and 25
h 16 and 36
Cheese slices are sold in packs of eight. Bread rolls are sold in packs of six. What is the least number of each pack that needs to be bought to have the same number of cheese slices and bread rolls?
7
MR
8
Find the HCF of each pair of numbers.
a 24 and 56
b 21 and 35
c 16 and 36
d 48 and 64
e 28 and 42
f 18 and 27
In prime factor form 1250 = 2 × 54 and 525 = 3 × 52 × 7.
a Which of these are common multiples of 1250 and 525? i 2 × 3 × 53 × 7
ii 23 × 3 × 54 × 72
iii 2 × 3 × 54 × 7
iv 2 × 3 × 5 × 7
b Which of these are common factors of 1250 and 525? i 2 × 3
ii 2 × 5
iii 5
iv 2 × 3 × 5 × 7
2
PS
9
The HCF of two numbers is 6. The LCM of the same two numbers is 72. What are the numbers?
PS
10
A = 2x2y and B = 3xy2.
a Work out the LCM of A and B. b Work out the HCF of A and B.
1.5 Prime factors, LCM and HCF
13810_P008_037.indd 29
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12/10/14 2:52 PM