Today was Catherine´s birthday. She turned 24. Catherine is twice as old as Ryan was when Catherine was as old as Ryan now. How old is Ryan now?..................
Application of divisibility Test to Problems
In a chemistry lab, a huge container contains 25399 litres of a liquid A and a chemist wants to split it into equal quantity and put it in different containers.
Those containers are at least 1/5th in size .How many such containers are required such that the number of litres of the liquid transferred to each of them is an integer?
Options:
A. 3 B. 9 C. 11 D. 10
This is problem is generally solved by dividing 25399 by each of the nos given in multiple choice and takes at least few mins to find the solution.
By applying divisibility, this problem can be solved in few seconds.
By looking at choices, we know 10 is not the answer.
We can apply test of divisibility by 3 :2+5+3+9+9 = 28 is not divisible by 3
If a number is not divisible by 3, it is not divisible by 9, as 3 is a factor of 9.
Applying test of divisibility by 11: sum of odd digits = 2 +3 +9 = 14 Sum of even digits: 5 +9 = 14.
Difference between sum of odd digits and even digits = 0. If the difference is 0 or divisible by 11, the number is divisible by 11.
