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Y is 0 for 19 cases :00 01 02 03 04 05 06 07 08 09 10 20 30 40 50 60 70 80 90
X is 9 for only 2 cases :09 90
probability of X=9 given Y =0 is 2/19 (IMO)
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Unravel

Quote:
Y = 0 for 00, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 01, 02, 03, 04, 05, 06, 07, 08, 09
Total 20 cases.
X = 9 only for 2 cases i.e. 09 and 90.

P(X=9, Y=0) = 2/20 = 1/10.


Are there total 20 cases or 19 cases?
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There are 100 cases, it appears. 00, 01, 02, ... ,98,99

The product must be zero and sum to 9.

There are two cases, 09, 90.

2/100
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