Answer:
Probability to pick 4 tiles which spell CATS will be
.
Step-by-step explanation:
We have 8 scrabble tiles A, B, C, D, R, S, T, U in a bag.
Probability to pick 4 tiles C, T, A, and S out of 8 tiles = 
= 
= 
= 
= 
= 70
So we can choose C, T, A and S tiles in 70 different ways but the probability to pick 4 tiles which spell CATS will be
= 
Therefore, probability to pick 4 tiles which spell CATS will be
.