I also got 17. But my approach was different.
Case I - ways when neither 4 nor 6 is selected = 5c5.
Case II - ways when either of the 2 ( #4or #6) is selected = 2c1*5c4.
Case III - ways when 4 and 6 are selected (here #5 is a must as 4 & 6
can't be adjacent and models are to arranged shortest to tallest. = 4c2 ( as #4,5,6 are to be selected )
Total ways, when 4 & 6 can't be adjacent and group is arranged from shortest to tallest = I+II+III = 1 + 10 + 6 = 17.
Can you pls. explain how did you get
Ways in which 4th and 6th are adjacent = 4
What's the official answer.