A drinks machine offers three selections – Tea, Coffee or Random (Either tea or Coffee) but the machine has been wired up wrongly so that each button does not give what it claims. If each drink costs 50p, how much minimum money do you have to put into the machine to work out which button gives which selection ?

3 Answers on this Question

1. You have to put just 50p.

   Put 50p and push the button for Random. There are only 2
   possibilities. It will give either Tea or Coffee.

   ? If it gives Tea, then the button named Random is for Tea.
   The button named Coffee is for Random selection. And the
   button named Tea is for Coffee.

   ? If it gives Coffee, then the button named Random is for
   Coffee. The button named Tea is for Random selection. And
   the button named Coffee is for Tea.

   Thus, you can make out which button is for what by putting
   just 50p and pressing Random selection first.

   Reply

2. Almost Deven,

   you need to spend 1$
   push Coffee ot Tea twice and you can be sure
   IF same beverage is given twice it’s not Random and other selection is Random

   Reply

3. Correct Deven,

   Reply