Question

Q. 11. How many words can be formed from letters
of word SCHOOL, whereas both O's not come togehter
Solution. ​

Answer 1

We solve the complementary problem of counting the arrangements where both the O's do come together. The number of permutations of s, c, h, oo and l is 5!. As the total number of permutations of all the letters, with 2 copies of 'o', is 6!/2! = 720/2 = 360, the number of required kind of permutations (with o's not coming together is 360–5! = 360–120 = 240.