a compnay wants to have 3 digit phone extensions with the 1st digit not being zero. how many phone extensions are possible?

Question

yuki · Answer

this is a straight forward counting principal problem.

yuki · Answer

this is a straight forward counting principal problem.

yuki · Answer

you have a 3 digit number so that you cannot use 0 on the first digit

yuki · Answer

so you multiply the number of digits you are allowed to plug in in each of the slots that you have.

yuki · Answer

in the first digit you are alloewd to plug in 9 numbers from 1 to 9

yuki · Answer

for the second and third, you have all digits, so 10 numers.

yuki · Answer

once you multiply all those numbers you have the answer