Let each different arrangement of all the letters of DELETED be called a word.
(a) How many words are possible?
(b) In how many of these words will the D's be separated?
Results will come later!
source: 1989 HSC
(a) How many words are possible?
(b) In how many of these words will the D's be separated?
Results will come later!
source: 1989 HSC
The more you suffer before the test, the less you will do so in the test! 
