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Assume that you are rolling 2 dice. the first one is blue and the second one is pink.
In how many ways can you roll a sum less than 5?
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The sum of 2: (1,1)
The sum of 3: (1,2), (2,1)
The sum of 4: (1,3), (2,2), (3,1)
In all, there are 1 + 2 + 3 = 6 possible outcomes for a pair of dice with the sum less than 5.
Solved and explained.