when a hole is made at the bottom of the container then water will flow out of it
The speed of ejected water can be calculated by help of Bernuolli's equation and Equation of continuity.
By Bernoulli's equation we can write

Now by equation of continuity


from above equation we can say that speed at the top layer is almost negligible.

now again by equation of continuity


here we have 


now speed is given by


 
        
             
        
        
        
As momentum / time = force 
so; time = 100÷15
so your answer is 6.7 !!
        
             
        
        
        
Answer:
V=Bh 
Explanation:
B h is used for rectangular solids and cylinders
 
        
             
        
        
        
This leads to a paradox known as the Gibbs paradox, after Josiah Willard Gibbs. The paradox allows for the entropy of closed systems to decrease, violating the second law of thermodynamics. A related paradox is the "mixing paradox".