Tim was given this calculator by a friend who knows how much Tim loves unusual and quirky items.
Somehow, the calculator has a fault. We suspect it came out of the manufacturing process with this fault. Basically, whenever you do a calculation and press the = sign, the answer that appears is 5 less than it should be. So 12 + 12 comes out as 19, and 5 x 5 comes out as 20.
However the fault is confined to the = sign. If you press 12 + 12 +.... at that moment you will see 24 in the screen. However if you then press 12 again, and then press =, you will get the answer 31, instead of 36.