Can you reconstruct the long division calculation from the 'skeleton'?
Find the five distinct digits N, R, I, C and H in the following nomogram
Given any 3 digit number you can use the given digits and name another number which is divisible by 37 (e.g. given 628 you say 628371 is divisible by 37 because you know that 6+3 = 2+7 = 8+1 = 9). The question asks you to explain the trick.
If a two digit number has its digits reversed and the smaller of the two numbers is subtracted from the larger, prove the difference can never be prime.
Each letter represents a different positive digit AHHAAH / JOKE = HA What are the values of each of the letters?
Take any pair of two digit numbers x=ab and y=cd where, without loss of generality, ab > cd . Form two 4 digit numbers r=abcd and s=cdab and calculate: {r^2 - s^2} /{x^2 - y^2}.
What is the sum of all the digits in all the integers from one to one million?
Can you explain what's happening with these numbers?
Explore the factors of the numbers which are written as 10101 in different number bases. Prove that the numbers 10201, 11011 and 10101 are composite in any base.
A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.
