Download Using primes to find HCF LCM File

Identify the prime numbers in the grid below.
There are 7 to find.
127
X 153
X 303
X
129
313
199 187
213
57
X X
X X
111
449
93
X 367 453
X
X
666
1
X 137 183
X 919
X
415
To use the prime factorisation of a
number
• Use a Venn diagram to sort information
• Use prime factorisations to find the lowest
common multiple of two numbers
48 = 2 x 2 x 2 x 2 x 3
60 = 2 x 2 x 3 x 5
HCF = 2 x 2 x 3 = 12
LCM = 2 x 2 x 3 x 2 x 2 x 5 = 240
Find the HCF and
LCM of the
following:
24 and 30
36 and 50
48
60
16 and 72
• Multiply the numbers in the overlap to get the HCF
• Multiply all the numbers in the Venn diagram to get the
LCM.
Using prime factors to find the HCF and LCM
Main Task Page 8, Exercise 1D
Starting
Q4
Securing
Q5-7
Applying
Q8/9
Spot the three mistakes
60 = 2 × 2 × 3 × 5
294 = 2 × 3 × 7 × 7
60
294
2
2
7
7
3
5
= 35
HCF of 60 and 294 =
2×3x7
LCM of 60 and 294 =
2 × 2 × 2 x 3 × 3 x 5 x 7 × 7 = 17640
Correct method
60 = 2 × 2 × 3 × 5
294 = 2 × 3 × 7 × 7
60
294
2
7
2
3
5
HCF of 60 and 294 =
2×3
LCM of 60 and 294 =
2×5×2×3×7×7=
7
=6
2940