Find the LCD for each pair of fractions? help me please?

Question

1/6, 5/21
4/9, 15/36

how do i solve those..please please please help i need this done by tomorrow and i have 5 other worksheets in math to finish...so please help..and be detailed...

Answer 1

The first step that needs to be taken when finding the LCD of a pair of fractions is listing the multiples of both numbers.
For example: multiples of 6 are.....
6,12,18,24,30,36,42,48,54,60 ect
multiple of 21 are.....
21,42,84 ect
Now when you look at the multiples of both numbers,you can clearly see that 42 is the lowest multiple of both 6 and 21.Therefore multiple the numerator and the the denominator of 1/6 by 7 and 5/21 by 2.
VOILA THERE YOU HAVE THE LCD!!!!

Answer 2

First find a common denominator that has a common factor, This is easily done by simply multiplying the two denominators. ie: 6x21=126 then check out to see if all four numbers have a common factor 21/126 and 30/126. In this case they do ; it's 3 . So you would then divide all four numbers by 3 and get 7/42 and 10/ 42. Therefore the lowest common denominator would be : 42
In the second case, , multiply 9x36which equals 324 as a common denominator.Then check to see if all four numbers have a common factor 144/324 and 135/324. In this case they do: it's 9 so you would divide all four numbers by 9 and get 16/ 36 and 15/36. This method will allow you to find the LCD for any large combinations of numbers. What you're looking for is a common denominator dividable by the same number so in the second case it's apparent that 9 is divisible by 9 and 36 is also.

Answer 3

[02]
6=2*3
21=3*7
LCM for 6 and 21=2*3*7=42
Therefore LCD is 42

9=3*3
36=2*2*3*3
LCM of 9 and 36
=2*2*3*3
=36
Therefore LCD is 36

Answer 4

1/6 = 7/42
5/21 = 10/42

4/9 = 16/36
15/36 = 15/36

Answer 5

42 and 36

Answer 6

42
36

Answer 7

5l8, 5l6