1) (a) y is directly proportional to x^2.It is known that y=

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1) (a) y is directly proportional to x^2.It is known that y=10 for a particular value of x.Find the value of y when this value of x is halved.
(b) seven men can paint a bridge in 15 days.
(I) How long would it take 3 men?
(II) The bridge was painted in t days.Write down an expression,in terms of t,for the number of men needed to paint the bridge.
2) A map is drawn to scale of 1:400000.
(a) Find the actual distance,in km,represented by 7cm on the map.
(b) A city covers an area of 800 km^2.Find,in cm^2,the area representing the city on the map.

1) .(a).y与x^2 成正比,x取某一特定值时 y=10,问,x缩小一半时,y=?
y=10/2^2=2.5
(b).(I).7人粉刷一座桥用了15天,问3人要多少天?
7*15/3=35 天
(II).若刷了t 天,需要多少人,用表达式表示；
人数=7*15/t,人数结果要取整进位.
2）地图比例是1:400000的.
1cm=4Km,1cm^2=16Km^2
(a).7cm对应地图是多少 Km?
7*400000/100000=28 Km
(b).某城市占地 800Km^2,在地图占多少cm^2
800/16=50cm^2

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