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52-card lottery (Posted on 2023-03-29) Difficulty: 3 of 5

Let a 52 deck of numbered cards be created as follows:

2 special cards: 0 and 1
25 powers of 2: 2, 4, 8, ..., 2^25
25 powers of 3: 3, 9, 27, ..., 3^25

Shuffle the deck and draw at random 3 cards. Evaluate the product of the 3 numbers, say P.

What is the probability of P=0?
What is the probability of P being a non zero integer square?
What is the probability of P being a 4-digit number?

No Solution Yet Submitted by Ady TZIDON    
Rating: 5.0000 (1 votes)

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Part 3 analytically | Comment 11 of 12 |

  0 1 2 3 4 5 6 7 8 9 10111213
0                    x x x x
1                  x x x
2 x x x x
3 x x x
4 x x x
5 x x x
6 x x x
7 x x x
8 x

The matrix above shows the powers of 2 and powers of 3

that lead to a 4 digit product.

Case 1: the 1 is drawn

subcase a: the other cards are both powers of 2: 4+5+5+6=20 ways

subcase b: one power of 2, one power of 3: 21 ways

subcase c: both powers of 3: 3 ways

Total case 1 = 47


Case 2: the 1 is not drawn

subcase a: all powers of 2: 4+5+7+8=24 ways

subcase b: two powers of 2, one power of 3: 13+14+8+5+4+1=45

subcase c: one power of 2, two powers of 3: 5+5+4+3+3+2+1+1=24

subcase d: all powers of 3: 3 ways

Total case 2 = 96


For a grand total of 143

143/22100 = 11/1700 = 0.00647


  Posted by Jer on 2023-03-29 14:21:18
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