Solution Step 0/0
In this stack of three regular dice, 13 faces are visible - 3 from each of the four sides and the 13th - the top one.
What is the sum of spots on the hidden faces?
What is the sum of spots on the hidden faces?
Explanations
Yes, it can be done.In a regular die the opposite faces add up to 7. Five faces are hidden:
a) two opposite faces in the bottom die (7 in total);
b) two opposite faces in the middle die (7 in total);
c) the face “3“ in the top die, as the opposite face to the visible “4“ face at the top.
(a) + (b) + (c) = 17.
The overall rule for such a challenge when three dice are stacked up is as follows:
21 minus the top visible face of the stack. This gives the sum of the spots on all the hidden faces in the stack.
[After Boris A. Kordemsky. The Moscow Puzzles: 359 mathematical recreations. 1972]
Check 17
Check 18
Check 19
Check 20
