请教两题

ninaluan

at a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. if the night crew has 4/5 as many workers as teh day crew, what fraction of all the boxes loaded by the two crews did theday crew load?
答案为5/8

in a certain game, a large container is filled wiht red, yellow, green, and blue beads worth, respectively, 7,5,3,2 points each. a number o fbeads are then removed from the container. if the product of the point values of the removed beads is 147,000, how many red beads were removed?
答案为2，

x is 40% ryegrass and 60% bulegrass by weight; y is 25% ryegrass and 75%fescue. if mixture of x and y contains 30% ryegrass, what percent of the weight of  this mixture is x?
答案：33（1/3）%
请指教一下！谢谢！

blueeyes

社白天每个工人搬箱数为d晚上每个工人搬箱为n  n=3/4d    人数之比为N=4/5D
Dd/(Nn+Dd)=5/8

(40%x+25y)/(x+y)=30%  2x=y   
x/(x+y)=1/3=33(1/3)%

kathy72

第1题

设白天有Y人，每人装卸Y箱，则白天装卸XY箱，晚上装卸(3/4)(4/5)XY, 则白天装卸的比例为XY/(XY+3/5XY)=5/8

第2题
147000＝7＾2＊3＊5＾3＊2＾3，因此红球2个。

第3题

X中　40%ryegrass    60% bulegrass
Y中  25%ryegrass    75%fescue

则　(40%X+25%Y)/(X+Y)=30%
表示为　（15%X＋25%（X＋Y））/(X+Y)=30%, X/(X+Y)可算出1/3