Math Brain Teasers · Billy-B
Math Brain Teaser #16
From Billy-B's legendary 1001 Puzzle Collection — preserved on Puzz.com since 1998.
Puzzle #16
If you have 3 dice that are shaped as a tetrahedron, a cube, & an icosahedron, & you rolled each of them, each die would display a number from 1-4, 1-6, & 1-20, respectively. Assume that the tetrahedron & icosahedron are regular. If there is an equal chance that a die will display any of its numbers each time it is rolled, what percent chance is there that the numbers rolled will total 7 if all three dice are rolled once, & the numbers they display are added together?
Reveal Answer
14/480, 7/240, or approximately 2.91%, as there are 14 situations where the dice will show a total of 7 out of 480 possible combinations.
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