v(ср)=S(весь)/t(весь)=2S/(t1+t2)
t=S/v
t1=S/600
t2=S/40
v(cp)=2S/(S/600+S/40)=2S/(16S/600)=(2S×600)/16S=75 (км/ч)
1
21/2=10.5
13/5=2.6
10.5*2.6=27.3
2
37/9=4.1
11/17=0.65
4.1*0.65=2.665
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