turkey-yks 2013 Q29

turkey-yks · Other · ygs Conditional Probability Combinatorial Conditional Probability (Counting-Based)
A bag contains 10 balls numbered from 1 to 10.
Given that the sum of the numbers on two balls randomly drawn from the bag is 15, what is the probability that ball number 7 was drawn?
A) $\frac { 2 } { 3 }$
B) $\frac { 2 } { 5 }$
C) $\frac { 2 } { 7 }$
D) $\frac { 1 } { 2 }$
E) $\frac { 1 } { 3 }$ 
A bag contains 10 balls numbered from 1 to 10.

Given that the sum of the numbers on two balls randomly drawn from the bag is 15, what is the probability that ball number 7 was drawn?\\
A) $\frac { 2 } { 3 }$\\
B) $\frac { 2 } { 5 }$\\
C) $\frac { 2 } { 7 }$\\
D) $\frac { 1 } { 2 }$\\
E) $\frac { 1 } { 3 }$
Paper Questions
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