Factors, multiples & primes: 11 Plus maths practice
Primes, HCF, LCM, squares and cubes.
CoreIn almost every paper that tests this subjectAbout 60 seconds a question in the test
The big idea
A factor divides exactly into a number; a multiple is in its times table. A prime number has exactly two factors: 1 and itself (1 is not prime).
The highest common factor (HCF) is the largest factor two numbers share; the lowest common multiple (LCM) is the smallest multiple they share.
Tips that save marks
Learn the primes to 100.
Use factor pairs to find all factors quickly.
For LCM, list multiples of the larger number and test them.
Now try five
Try each one before you look at the answer: answering from memory is what makes it stick. Tap an option to check it. Most children get three or four right at first; five out of five means move on to the next topic.
Question 1Aim for about 60 seconds
Which number belongs in the box marked ?
Multiples of 4
Not multiples of 4
Numbers greater than 20
40, 36
26, 35
20 or less
?
11, 7
Show the worked answer
Answer: B, 4
How to work it out
The ? box is in the row “20 or less” and the column “Multiples of 4”.
4 fits both.
Why the other options are wrong
A (34): This fits neither label of the ? box.
C (40): This fits “Multiples of 4” but not “20 or less”.
D (10): This fits “20 or less” but not “Multiples of 4”.
E (32): This fits “Multiples of 4” but not “20 or less”.
Question 2Aim for about 60 seconds
What is the lowest common multiple of 5 and 3?
Show the worked answer
Answer: C, 15
How to work it out
Count up in 5s and 3s until they meet: 15.
Question 3Aim for about 60 seconds
What is the highest common factor of 9 and 6?
Show the worked answer
Answer: D, 3
How to work it out
List the factors of each and find the largest they share: 3.
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