1、设X千米.(1/7)x+(1/7)x+16=94 x=273km
2、设X千米.(1/7)x+(1/7)x+16=x-94 x=154km
3、设全长x米.(1/3)x-12+(1/4)x+15+102=x x=252m
乙修了:(1/4)*252+15=78m
4、R=15.42/(3.14+2)=3cm,S=3.14*3^2*(1/2)=14.13cm^2=0.1413dm^2
5、设大圆半径r,则小圆半径(3/5)r,(r^2-(0.6r)^2)*3.14=64
r^2=100/3.14 S=3.14*(100/3.14)=100cm^2
6、设半径为R.那么长方形的长为:2*根号下(R^2-(1/4)R^2)
(2*根号下(R^2-(1/4)R^2)+R)*2=24.84
解得R,求S=πR^2=65cm^2
7、设师傅要做x个,则徒弟做140-x个.
0.8(140-x)+0.75x=140-32
解得x=80个,徒弟60个.
8、C=6+3*3.14=15.42dm
S=(1/2)*3.14*3^2=14.13dm^2