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Two people have an appointment to meet from 8 to 9. If they don't come, wait 15 minutes and ask them the probability of meeting.

Do it in plane coordinates

Make a plane coordinate system XOY, and express the arrival time of two people with x and y.

X and y belong to (0, 1), which means between 8 o'clock and 9 o'clock respectively.

The total range of x and y is a square with a side length of 1.

The qualified range is LX-yl.

Qualified area =1-3/4 * 3/4 =1-9/16 = 7/16.

So the probability of meeting = (7/16)/1= 7/16.