Page 38 - NUMINO TG_5A

02Factors Unit

a. b.

24 = 1 24 42 = 1 42 36 = 1 36 63 = 1 63 When the numbers created are greater than
12 = 2 12 12 = 2 21 =2 18 =3 21 20, it is difficult to predict which numbers
12 = 3 8 12 = 3 14 =3 12 =7 9 will divide the numbers equally. The factors
12 = 4 6 12 = 6 7 =4 9 can be found by finding how the products
=6 6 are made by multiplying two numbers.

Number of Number of Number of Number of The following error may be made when
factors: 8 factors: 8 factors: 9 factors: 6 finding factors.
When writing multiplication sentences to find
c. d. the factors of 24, the following is written:
1 24, 2 12, 3 8, 4 6, 6 4, 8 3,
12 2, 24 1
This can be misinterpreted to say that 24
has 16 factors. Show the students that a
factor of the same number is only counted
once.

58 = 1 58 85 = 1 85 27 = 1 27 72 = 1 72
=2 29 =5 17 =3 9 =2 36
=3 24
=4 18
=6 12
=8 9

Number of Number of Number of Number of
factors: 4 factors: 4 factors: 4 factors: 12

2. Factors 13

Problem: Find all of the numbers from 1 to 15 that only have two factors.
Answer: 2, 3, 5, 7, 11, and 13.
Solution: Numbers that only have two factors have the factors of 1 and itself. Find the numbers from 1 to 15

whose factors are only 1 and itself.

1 1 1( ), 2 1 2( ), 3 1 3( ), 4 2 2( ), 5 1 5( ),
6 2 3( ), 7 1 7( ), 8 2 4( ), 9 3 3( ), 10 2 5( ),
11 1 11( ), 12 2 6( ), 13 1 13( ), 14 2 7( ), 15 3 5( )

The numbers that only have two factors are 2, 3, 5, 7, 11, and 13.

5A Unit 02 021