if it randomly rains on 3 of the 7 days next week, what's the probability of a rain-free weekend?

Question

this is a stats question

Answer 1

Total number of ways to choose 3 days out of 7 is 7!/(3!4!) = 35
The number of "good" ways (no rain in the weekend) is 5!/(3!2!) = 10
The probability is 10/35= 0.286

Answer 2

It partially depends on your definition of weekend. I am going to assume you mean Saturday and Sunday, but not Friday.

Here are the possibilities. The numbers represent the days of the week, 1 being Monday.

123 * 124* 125* 126 127 134* 135* 136 137
145* 146 147 156 157 167 234* 235* 236
237 245* 246 247 256 257 267 345* 346
347 356 357 367 456 457 467 567

10 out of the 35 have no 6 or 7, which is 28.57%. If you take the Fridays (5) out too, it gets even lower: 4/35, or 11.43%

Answer 3

It's the number of ways it can rain 3 times in 5 days divided by the number of ways it can rain 3 times in 7 days.
(5!/(2!*3!))/(7!/(4!*3!)) = 28.57%

Doug

Answer 4

I would say 50:50, because nature can not be controlled by statistics.

Answer 5

Ask Murphy....