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Multiplication. Printable worksheets. Factors and Prime numbers.

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Factors and Prime numbers

Worksheet reference: T00997-WKyAp
Factors of a number divide exactly into that number with no remainder. Hence 4 is a factor of 12, 4×3=12. While 5 is not a factor of 12. 5×2=12. 2 remainder 2.
A prime number has only two distinct (different) factors, itself and 1. One (1) is not a prime number because it's factors are not distinct. It has just one factor, itself.
To find the prime numbers up to 100.
12345678910
11121314151617181920
21222324252627282930
31323334353637383940
41424344454647484950
51525354555657585960
61626364656667686970
71727374757677787980
81828384858687888990
919293949596979899100
Shade the number 1 which is not prime. Ignore 2, but shade in the rest of the numbers in the two times table. Use a different colour. Ignore 3, but shade in the three times table in a different colour. Now do the same with 5, 7. The numbers that are not shaded are the prime numbers. The method is called the sieve of Eratosthenes.
You can find pairs of factors of any number by dividing by any of the primes. You can use a calculator.
Example: 70 = 2 × 35 or 5 × 14 or 7 × 10;
These are the factor pairs.
Find the factor pairs for each of the following numbers. Decide if the number is prime.
A)
624
____________________
B)
402
____________________
C)
950
____________________
D)
657
____________________
E)
891
____________________
F)
118
____________________
Most numbers have even number of factors. Which numbers have an odd number of factors? What is the name of this group of numbers?
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ANSWERS
Factors and Prime numbers

T00997-WKyAp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
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24
25
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27
28
29
30
31
32
33
34
35
36
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38
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40
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46
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48
49
50
51
52
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100
A)
2 × 312 or 3 × 208 or 4 × 156 or 6 × 104 or 8 × 78 or 12 × 52 or 13 × 48 or 16 × 39 or 24 × 26
B)
2 × 201 or 3 × 134 or 6 × 67
C)
2 × 475 or 5 × 190 or 10 × 95 or 19 × 50 or 25 × 38
D)
3 × 219 or 9 × 73
E)
3 × 297 or 9 × 99 or 11 × 81 or 27 × 33
F)
2 × 59
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