A reasonable estimate is an educated guess made by an observer based on that person's current knowledge and following observations. For example, If Garth knew that he was 1.2 meters tall, and he observed that the door was approximately twice his own height, Garth could then make the reasonable estimate that the door is about 2.4 meters tall.
        
             
        
        
        
5^4/5
Multiply the number by it's exponent
625/5
Divide
Final Answer: 125
        
             
        
        
        
We have to give counter example for the given statement:
"The difference between two integers is always positive" 
This statement is not true. As integers is the set of numbers which includes positive and as well as negative numbers including zero.
Consider any two integers say '2' and '-8'. Now, let us consider the difference between these two integers.
So, 2 - 8
= -6 which is not positive.
Therefore, it is not necessary that the difference of two integers is only positive. The difference of two integers can be positive, negative or zero.