Write fraction in simplest form

Question

A. 18/90 B. 28/42 C. 16/40 

Answer 1

A. What number do 18 and 90 have in common? Both are divisible by 2 as well as by 3 using the divisibility rules. As such, that means they are also divisible by 6. However, it should also be apparent that both are divisible by 9 because:

 

18 = 2 x 9

90 = 10 x 9

 

So 18/90 reduces to 2/10 if we divide both numerator and denominator by 9. However, both 2 and 10 are even, which means they are both divisible by 2. So, we ultimately end up with 2/10 = 1/5.

 

Use the same thought process for B and C.

 

What factors do 28 and 42 have in common? 

What factors do 16 and 40 have in common?

 

Let me know if you have any questions. Thanks!