请教两道数学题。实在读不懂题...

今天也要加油鸭 · 发表于 2018-12-7 10:55:07

1.Car B starts at point X and moves clockwise around a circular track at a constant rate of 2 mph. Ten hours later, Car A leaves from point X and travels counter-clockwise around the same circular track at a constant rate of 3 mph. If the radius of the track is 10 miles, for how many hours will Car B have been traveling when the cars have passed each other for the first time and put another 12 miles between them (measured around the curve of the track）？
我对MPH这个单位不是很确定。主要我感觉这道题至少要考虑圆的周长吧，毕竟是在圆上跑，但是答案没有...

2.A new tower has just been built at the Verbico military hospital; the number of beds available for patients at the hospital is now 3 times the number available before the new tower was built. Currently, 1/3 of the hospital's original beds, as well as 1/5 of the beds in the new tower, are occupied. For the purposes of renovating the hospital's original wing, all of the patients in the hospital's original beds must be transferred to beds in the new tower. If patients are neither admitted nor discharged during the transfer, what fraction of the beds in the new tower will be unoccupied once the transfer is complete？

这道题真看不懂了...

spicytaco · 发表于 2018-12-7 11:14:29

1.mph=miles per hour =miles/h

20pi

相遇的时刻：2*10+2t+3t=20pi 那么 t=8.6
拉开12mile的时刻： 2t1+3t1=12 那么t1=2.4

t+t1=11
或者直接合并

2*10 +2t+3t=20pi+12 得出t=11

看错了 b先离开哦那就加上10个小时 T=11+10=21

alanalan2 · 发表于 2018-12-7 11:19:48

1、
A出发时两车距离20π-20，从A出发到与B相遇需要4π-4小时，加上B已经开的10小时，以及两车再次相距12需要12/(2+3)=2.4小时，最后B跑的总时间为4π+8.4小时

2、
假设原来医院中有x张床，那么新建的tower里有2x张床，这样总数就是3x张床（3 times the number available before the new tower was built）
现在原医院中x张床被占了1/3，就是有x/3人，tower里的床被占了1/5，就是有2x/5人，全部搬到tower中的话，tower中有了x/3+2x/5=11x/15人
tower中原本有2x张床，没被占的床的fraction就是(2x-11x/15)/2x=19/30

spicytaco · 发表于 2018-12-7 11:20:36

2. 设原来是x
现在就是3x...那么新的bed就是2x

旧bed的三分之一就是1/3x
新bed的五分之一就是2x*(1/5)=2x/5

把1/3x的旧床转移到新床
1/3x + 2x/5 = 11x/15

新床的占有率就是11x/15 除以2x 等于 11/30哦哦非占有率啊就是19/30

今天也要加油鸭 · 发表于 2018-12-7 13:45:30

spicytaco 发表于 2018-12-7 11:20
2. 设原来是x
现在就是3x...那么新的bed就是2x

懂了谢谢啊！死就死在看不懂题了。

今天也要加油鸭 · 发表于 2018-12-7 13:47:05

alanalan2 发表于 2018-12-7 11:19
1、
A出发时两车距离20π-20，从A出发到与B相遇需要4π-4小时，加上B已经开的10小时，以及两车再次相距12需 ...

突然明白了第一题我怎么死活看不懂解析了。因为答案和你写的一样以至于让我把pai看成了n...我就是瞎

请教两道数学题。实在读不懂题...

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