Al had forgotten his locker combination and was going to be late for class.
But he was able to remember the following things:
- Each of the three numbers of the combination can be anywhere between 1 and 39 inclusive.
- Each one was different and the sum of the first two numbers was 42. The last two numbers differed by only two, and all three numbers were primes.
His friend remembered the combination and told him, "If you take the three numbers of your combination and multiply them together, the last digit of the product will be ....", and then whispered something in his ear.
With that, Al was able to deduce his combination and open his locker.
What was his combination?
37,5,3 opens the locker, 5 at the end being unique.
13*29*31 & 29*13*11
produce 7 at the end
while 11* 31 *29 &
23*19*17 produce 9 .