Question

Why 4/10 and 40/100 have unlike denominators but are equivalent fractions.

Answer 1

because you can simplify 40/100 and get 4/10
when you divide 40/100 by ten on the den. and num. you will get 4/10

Answer 2

They are equivalent fraction because both fractions have a common factor of 4/10.
You can divide 4/10 and get 1; 40/100 and get 10. Fractions are equivalent if they have common factors.