What number is one fifth of one fourth of one ninth of 900? 2 3 4 5 6 7 none of these i don't know?

First, we want to write an expression for what is given:

(1/5) (1/4) (1/9) (900)

Now, we can solve this. Remember that to multiply fractions, we can just multiply the numerators and the denominators. Also, whole numbers always have a denominator of 1.

(900/180)

=5