Answer:
Step-by-step explanation:
You know that 9 = 10 - 1.
Then 9 of something is equal to 10 of it less one of it. Here, that "something" is four.

_____
<em>Comment on this math</em>
This illustrates a shortcut for multiplying by 9 that can be convenient for mental arithmetic. The idea is to multiply by 10, which just involves adding 0 (or moving the decimal point), then subtract the original number.
Least common denominator is 10
Answer:
14
Step-by-step explanation:
the diameter is the radius multiplied by 2
Answer:
5.243 is less than 5.4....
I'm not 100% sure if I'm doing it the right way, but I think the answer is the factorial of the number of letters divided by the factorials of the number of elements of each kind of element (in this case, the same letters)
9!/1!4!1!2!1!
= 9 · 8 · 7 · 6 · 5 · 4!/4!2!
= 9 · 8 · 7 · 6 · 5/2
= 9 · 4 · 7 · 6 · 5
= 63 · 120
= 7,560 permutations