Holiday time

ob · 发表于 2004-11-6 01:17:28

A group of friends went on a holiday to a hill station. It rained for 13 days. But when it rained in the morning, the afternoon was lovely. And when it rained in the afternoon, the day was preceded by clear morning.

Altogether there were 11 very nice mornings and 12 very nice afternoons. How many days did their holiday last?

ac_x · 发表于 2004-11-6 07:19:23

18 days.

since there exist some day that doesn't rain at all.

Those days will have both nice mornings and afternoons.

suppose 11 mornings are coresponding to 11 afternoons, we will get 1 raining day. 12 days in total

suppose 10 mornings are coresponding to 10 afternoons, we will get 3 raining days. 13 days in total

...

then from the patern, we will get 5 mornings are coresponding to 5 afternoons, and get 13 raining days[tuh, duh, mathes]. and that will result 18 days in total.

ac_x · 发表于 2004-11-7 08:00:39

answer is above

ob · 发表于 2004-11-7 10:04:20

There is another way to do it:

Total days= (rainy morning+rainy afternoon +shiny morning +shiny afternoon)/2

since the total of the first two terms is 13 and shiny morning is 11, shiny afternoon=12, the # of holidays=(13+11+12)/2=18

ac_x · 发表于 2004-11-7 10:52:55

thanks for letting me know :D

i have never thought in that way .hehe

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Holiday time

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answer is above

Good![:)]

回复：Good![:)]