43/100 - 223/100
(43x100)-(23x100)/100x100
-18000/100000
(-18000/2000)/(100000/2000)
= -9/5 or -1 4/5
If nCk represents the number of ways k parts can be chosen from a pool of n, the probability of interest is the complement of the probability of selecting all good parts.
1 - (167C3)/(170C3) = 42,085/804,440 ≈ 0.0523
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nCk = n!/(k!(n-k)!)
You should divide when converting a larger unit to a smaller unit.
Draw a line through the x axis at x=3 and shade in everything to the left of x=3. That is your graph.