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Prime numbers are numbers that have exactly two factors: one and the number itself.
Composite numbers are numbers that have more than two factors.
You can think multiples of a number as the” times table” for that number. For example: the multiplies of 3 are:
3 × 1 = 3, 3 × 2 = 6, 3 × 3 = 9 and so on.
A multiple of a number is found when you multiply that number by a positive integer. The first multiply of any number is the number itself (the number multiplied by one).
**INTEGER** Any of the negative and the positive whole numbers including zero.
Worked example 1
a) Which are the first 5 multiples of 7?
b) Is 280 a multiple of 4?
c) Is 363 a multiple of 5?
Solution
a) To find these, multiply 7 by 1, 2, 3, 4 and 5.
7 x 1 = 7
7 x 2 = 14
7 x 3 = 21
7 x 4 = 28
7 x 5 = 35
Answer: The first 5 multiples of 7 are: 7, 14, 21, 28, 35.
b) To find out divide 280 by 4. If it goes exactly, then 280 is a multiple of 4.
280 : 4 = 70.
Answer: 280 is a multiple of 4.
c) To find out divide 363 by 5. If it goes exactly, then 2363 is a multiple of 5.
363 : 5 = 70, reminder 13.
Answer: No, 363 isn’t a multiple of 5.
Worked example 2: Find the lowest common multiple of 4 and 6.
Solution: List several multiples of 4 (M4).
M4 = 4, 8, 12, 16, 20, 24, 28, 32
List several multiples of 6 (M6).
M6 = 6, 12, 18, 24, 30, 36, 42
Find the lowest number that appears in both sets. This is LCM
Answer: LCM = 12
A factor is a number that divides exactly into another number with no reminder. For example, 3 is a factor of 24 because it goes into 24 exactly 8 times. The number 1 is a factor of every number. The largest factor of any number is the number itself.
The highest common factor of two or more numbers is the highest number that is a factor of all the given numbers.
Worked example 3:Find the HCF of 16 and 24
Solution:List the factors of each number and underline the factors that appear on both sets.
F16 = 1, 2, 4, 8, 16
F24 = 1, 2, 4, 6, 8, 12, 24
Pick out the highest underlined factor.
Answer: HCF = 8
Prime numbers are numbers that have exactly two factors: one and the number itself.
5 is an example of a prime number because it has exactly two factors. The number itself 5 and the number 1. So, it can’t be divisible by any other whole number without having a reminder.
Composite numbers are numbers that have more than two factors.
15 is an example of a composite number because it has more than two factors. The factors are 1, 3, 5, 15. Our number can be divisible by each of this numbers without having a reminder.
See more about prime numbers here
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Prime numbers are numbers that have exactly two factors: one and the number itself.
Composite numbers are numbers that have more than two factors.
Next article
Prime numbers are numbers that have exactly two factors: one and the number itself.
Composite numbers are numbers that have more than two factors.