Am not a friend with this isssue:
6 red, 1 black and 3 white balls
We draw 3 balls in a raw, returning the
drawn ball each time.
How many different results which include
at least one black ball.
Way_1 : 1000−9^3 = 271 results That′s very ok
Way_2 : 1×9×9_(very ok) ×3_(Omg, Why?)
+ 1×1×9×3_(the same confused above)
+ 1×1×1_(very ok and i like it.... but why not ×3)
= 271 result
Explanation_(about the story of ×3) ?
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