1.顶顶和宁宁各有一盒棋子,两盒棋子共有270颗.顶顶拿出自己的25%给宁宁,宁宁的棋子正好比原来增加了20%.两人各原

设丁丁有x颗,宁宁有y颗
x+y=270
25%x+y=120%y=》5x=4y x=4y/5
代入得
4y/5+y=270
9y/5=270
y=150
x=120
所以
顶顶有120颗,宁宁有150颗.

丁丁原来20

Advantages 1.Use vertex at the top of the hydraulic,resolves the position is not firm problem,and positioning fast,only 10 seconds or so and vertical level can be fixed.Advantages 2.Use two root ZhiZi and traditional rbis combined with the laser positioning slow,solve the difficult,positioning of the problem of the great error.Advantages 3.Use the ashes of the conveyor belt upward transportation way forward and can change the perspective of big wipe board union,completely put reach the summit,not a mm.Advantages 4.Use vibrators on board to solve the increasing artificial wall with easy to appear empty drum,crack,issues in the metope of external thermal insulation thickness largest water up to 3 cm,the minimum thickness of plastering 0.3 cm.Advantages 5.Use can change the perspective of on board,the machine can't solve along the way the problem of pressure drop light.Advantages 6.Use in more convenient you pull rod of different height free docking,and solved the adjustable stem not through construction of the hole,and the machine to the site,insert made stem can use,without assembly.Pulling out made stem can transport,do not need to remove.Advantages 7.Machine operation 80 cm wide,the one side wall that 80,80 on the past 20,30,50 left centimeters wide,you only need to fill out a side,no adjustment,sealing block.Because of long time in sand ash inside,any adjustments,sealing block all is impossible.Advantages 8.Machine of belt can single stop,such as the construction hole and then sent ash,can wipe construction hole above.Advantages 9.With matching limit card hoop,card to and lintel coequal height can wipe lintel below.The same,with both hands hold on board the Angle change two root jue stem to below the window,can wipe window below.Advantage 10.Wipe the board design than the wide,so Yin Angle,Yang angles are all very easy to do a

A

A是正确的.
跌倒开关S是属于常开开关,只有在取暖器站立时跌倒开关才是使用常闭开关.在如图中B C 是使用跌倒开关S常开开关,它是不通电的,只有A D 才 是使用跌倒开关的常闭开关.但是图D中任意一个开关（S1 S2 S ）不闭合都不会通电,就不存在冷风与热风选择.图A 在闭合S1与S时就是送冷风,同时闭合S1 S2 S 时就是送热风.
我教你怎么看常开与常闭,如图开关S的黑粗线在线路图中的细线上面就是使用常开的开关,在线路图下面就是使用常闭开关.
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原来小胖（ 34 ）本,小亚（ 28 ）本,小丁丁（28 ）本?
90÷3=30
小胖30+10—6=34本
小亚30+8—10=28
小丁丁30—8＋6=28