How to find the common denominator of 2/4 and 1/5?

What's 4 x 5? It would be 20.

20 is answer

However 2/4 = 1/2
Common denominator of 1/2 and 1/5 is 10

You have to get a common denominator. You figure out what you can evenly divide 4 and 5 into...that would be 20. You convert the fractions by dividing the denominator into the 20 and how every many times it goes into it, you multiply that by the top. It goes into 20 five times. 5 times 2 is 10. 2/4 = 10/20. You just run up the multiplication tables until you get to one that works for both. 5...10...15...20...oh yea, four works there too.

As given, if you just look at the denominators, you have 4 and 5.
Since 4 and 5 share *no* factors, the lowest common denominator would just be 4 x 5 = 20.

However, this is a bit of a trick question. 2/4 can be reduced to 1/2. So you really should be finding the common denominator of 1/2 and 2/5. Again they have no factors in common, so the common denominator would be 2 x 5 = 10.

1/2 = 5/10
1/5 = 2/10

5/10 + 2/10 = 7/10

Answer:
Using a common denominator of 10 you get a sum of 7/10.

Multiply the denominators of 2/4 and 1/5. Then multiply each numerator by the other fraction's denominator, and swap out both denominators for the common denominator you found by multiplying the denominators of 2/4 and 1/5. Then if your numerator is an even number or one divisible by a number that the denominator is also divisible by, simplify it.

20, 40, 60 are good examples. 20 is the lowest common denominator

multiply the two factors (4 and 5) together

first of all look at their factors:
4: 1, 2, 4
5: 1, 5
except 1, there are no common factors, so you have to multiply them to get a comm denominator.
so 5*4=20