find mean proppotinals between 2 and 54

If a:b: :b:c then b^2=ac here b is called mean proportion. a=2, c=54 then b=√2×54=6√3

A man is travelling with 3 boxes with 30 chocolates in each box. During his journey he encounters 30 toll booths. Each toll booth inspector takes one chocolate per box that contains chocolate as tax. what is the largest number of chocolates he can be left with after passing through the toll booths.

Bro the answer is 25 The salesman goes through first 10 toll gates and he loses 10×3= 30 chocolates Then he has now 2 boxes of 30 chocolates then he goes through 15 toll gates and gives away 15×2= 30 chocolates and now he has 30 chocolates left so he passes through remaining 5 toll gates giving away 5 chocolates thus he is left with 25 chocolates