Answer:
The answer is 6:1 .
Explanation:
We don't need to have prior knowledge of combination or permutation.
Count the way to chose 4 letters.As given in the question chose sequence of different letters
For first place we have 10 letter
For second place we have 9 letter as one is already out
For 3 place we have 8 letter as two letter are already out
For 4 place we have 7 letter as three letter are already out
Total group of 4 letters = 10 * 9 *8*7
Similarly form group of 5 letters we have
Total group of 5 letters = 10 * 9* 8 * 7*6
then Calculating ratio between 4 and 5
We have,
Group 5 : Group 4 ::10 * 9* 8 * 7*6:10 * 9 *8*7
: : 30240 : 5040
divide by 5040 on both side we get
Group 5: Group 4 :: 6 : 1
