Can you replace the X (both small and big x) with the numbers between 1 to 19 such that all the rows of 3 numbers between X (big x) sum to 23 ?
Is it possible to write down 1,2,3..100 in some order (one after an other), such that the sum of any two adjacent numbers is a prime number?
Using the digits 1, 2, 3 and 4, find the number of 10-digit sequences that can be written so that the difference between any two consecutive digits is 1.
Examples of such 10-digit sequences are ********** and **********.
Complete the square with the numbers 1 to 5 so that no row, column or diagonal line of any length contains the same number more than once. What number must replace the question mark?
