how do you figure out the number of permutations in words?

Question

Letters in the word YELLOWKNIFE?

Answer 1

If all 11 letters were different then the answer would be 11!, or 11*10*9*...*3*2*1= ?

However, there are 2 E's and 2 L's.

The formula is (11!)/(2!)(2!)=(11*10*...*2*1)/(2*1)(2*1)=(11*10*9*8*7*6*5*3*2*1)= ? (the 4 in the numerator cancels with the 2*2 in the denominator) Multiply all the numbers to get the answer.