If ABC and DEF are both 3-digit numbers such that A, B, C, D, E and F are distinct non-zero digits such that ABC + DEF = 1111, then what is the value of A + B + C + D + E + F ?

Three of the five positive integers p, q, r, s, t are even and two of them are odd (not necessarily in order). Consider the following :

1. p + q + r - s - t is definitely even.

2. 2p + q + 2r - 2s + t is definitely odd.

Which of the above statements is/are correct?

If p, q, r and s are distinct single digit positive numbers, then what is the greatest value of (p + q) (r + s)?

Each digit of a 9-digit number is 1. It is multiplied by itself. What is the sum of the digits of the resulting number?