What is the Least Common Denominator of 7,11,9 and 20?

Break down the numbers into their prime factors.

7 = 7
11 = 11
9 = 3 x 3
20 = 5 x 2 x 2

Since there are no identical numbers in a column, we just multiply it like that to get the LCD. 5 x 2 x 2 x 3 x 3 x 11 x 7 = 13860

LCD is 13860. Hope this helps.

7(11)(9)(20) = 13,860

7 ..= ..............................7
11 = ...................................11
9 ..= ............3 x 3
20 = 2 x 2 ............x 5
-------------------------------------------
.....= 2 x 2 x 3 x 3 x 5 x 7 x 11
.....= 13860

13860

7*9*11*20 = ?

Use the prime factors to figure it out.

7: 7
11: 11
9: 3×3
20: 2×2×5

Multiply all factors that are not common to them all. In this case, none are common, so the simplest LCM is the product of them all: 13,860

All are integers so their denominators are 1 each. SO that itself is the LCD.
Other answer gives you their LCM not LCD.