Answer: 210
Step-by-step explanation:
We know that the number of combinations of n things taken r at a time is given by :-
So, number of ways to select 3 plants out of 7 =
Also number of ways to arrange them in 3 positions = 3! = 6
Now , total number of arrangements with 1 plant in each spot = (number of ways to select 3 plants out of 7) x (number of ways to arrange them in 3 positions)
= 35 x 6
=210
Hence, required number of ways = 210