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# GMAT: Math 45

214-216, pg. 181. Created by Sal Khan.

## Want to join the conversation?

• Doesn't Q217 state 60 pairs rather than 30?
• If the last question says that there are 60 sibling pairs, then that means that there's 60 siblings in either school and not 30 siblings in either like Sal illustrated. That means that the chances for finding a sibling from School J is 60/1000 or 6/100, then to get that sibling's sibling is still the same chance, so our chance gets multiplied by 1/800, which gives us a resulting chance for randomly picking out a sibling pair from the two schools of 6/8000, or after simplifying by 2 - 3/4000.

So, yes, you're correct. It was just a simple mistake from Sal's point.
(1 vote)
• What if the question is asking for the greatest#? What's the answer? I just want to make sure I really understand this.