Question

determine the common factors of the given number. 15 and 25, 28 and 42, 15, 20 and 30, 20, 30 and 40.​

Answer 1

Step-by-step explanation:

15-1,3,5,15

25,1,5,25,

28-1,2,4,7,14,28

42-1,2,3,6,7,14,21,42

20-1,2,4,5,,10,20

30-1,2,3,5,6,10.15,30

40-1,2,4,5,,8,10,20,40

Answer 2

Answer: for 15 & 25 common factor is 5

for 28 and  42 it is 14

for 15 , 20 and 30 it is 5

for 20 , 30 and 40 it is 10

Step-by-step explanation

to find common factors of given number  ,say 15 , 20,30

first decompose all numbers into the product of prime factors ,

like 15=3*5 , 20=2*2*5 , 30=2*3*5

now take out all the common prime factors

here the common prime factor is 5 only

so in this case the common factor is 5

for 28 and 42

28=2*2*7 and 42=2*3*7  here common prime factors are 2 and 7

so the final common factor is 2*7 that is 14