a+b+c=odd b+c+d=odd ADD a+2b+2c+d=even a+d=even
If a, b and c are integers, is it possible that a+b, b+c and c+a are all odd numbers? Explain with your working....
A, B, C and D are four positive numbers such that A is 2/3 times of B, B is 5/6 times of C and C is 3/5 times of D. If the average of 3 times of A and 4 times of D is 900, then what is the average of all four numbers A, B, C and D?
If a, b, c and d are distinct pairwise co-prime positive integers such that a^2 + b^2 = c^2 + d^2, find the lowest possible value of a + b + c + d?