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knight247
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In a certain bus, seats are arranged such that there are 4 in each row: 2 are to the left of the central aisle and 2 are to the right of the central aisle. Seats are considered to be "next to one another" only if they are in the same row and on the same side of the aisle. If the bus has 10 rows of seats, what is the probability that two randomly chosen seats are in the same row but are NOT "next to one another"?
OA is [spoiler]2/39[/spoiler]
Here is how i solved it:
Total number of possibilities is 40C2=780
Now to find two seats in the same row, we first pick any one out of the 10 rows in 10C1 Ways
Now in this row, we pick any one seat in 4C1 ways.
Now, the next seat we pick has to be on the other side of the aisle, so we pick the next one in 2C1 ways.
Altogether we have 10C1*4C1*2C1= 80
80/780=8/78=4/39
I'm getting an additional 2 somewhere. Hoping to get a clarification. Thanks
OA is [spoiler]2/39[/spoiler]
Here is how i solved it:
Total number of possibilities is 40C2=780
Now to find two seats in the same row, we first pick any one out of the 10 rows in 10C1 Ways
Now in this row, we pick any one seat in 4C1 ways.
Now, the next seat we pick has to be on the other side of the aisle, so we pick the next one in 2C1 ways.
Altogether we have 10C1*4C1*2C1= 80
80/780=8/78=4/39
I'm getting an additional 2 somewhere. Hoping to get a clarification. Thanks
