Question

Find the number of four letter word that can be formed from the letter of the word $HISTORY$ .(each letter to be used atmost once)
How many contain the letter $Y$?

Answer 1

total number of different types of letters = $7$

we have to make a $4$ letter word that contains y ,

one place is fixed for y and let it be first place

no. of ways it can be done = $6\times 5\times 4$

y will also permutate so,

=$4\times 30\times 4!=2880ways$