







4821x14y is an 8digit number divisible by 72 
20140806 

From RAYA: if 4821x14y is an 8digit number divisible by 72. How many values can x and y take? Answered by Penny Nom. 





A 4 digit number 
20140404 

From LIM: "A" is a 4 digit number formed by all the numbers from 1 to 4. When "A" is divided by 9, the remainder is the biggest possible value. What is the biggest value of A? Answered by Chris Fisher. 





An even multiple of 27 
20110201 

From parth: the 6 digit # 63x904 is an even multiple of 27 what is X Answered by Penny Nom. 





Powers 
20101020 

From dylan: how do you write 20736 in exponential form .same for 1728 and 50625.
is there a formula to figure out how to express large know numbers in exponential form. Answered by Penny Nom. 





Divisibility rules 
20010907 

From A student: Why is it that when you add the digits of a number you can tell what the multiples of that number are. Example: 12131313111,
1+2+1+2+1+3+1+1+1=18,
therefore 12131313111 is divisble by 2, 9, 18, & 3 because those numbers are divisble by 18. Answered by Penny Nom. 





Divisibility by 9 
20001024 

From Kelera: If the sum of the digits of a number is divisible by 9, then the number itself it divisible by 9. Why is that? How do you explain this? Answered by Penny Nom. 





Divisibility by 3 
20000324 

From Pat Walsh: W hy does it work when you add the digits of a number then divid by three to see if the number is divisible by three Answered by Penny Nom. 





Divisibility by 9 
19990221 

From Razzi: I've been having a hard time trying to solve the following problem and I was wondering if you could help me. For any positive integer a let S(a) be the sum of its digits. Prove that a is divisible by 9 if and only if there exist a positive integer b such that S(a)=S(b)=S(a+b). Answered by Chris Fisher and Harley Weston. 

