Tell me please!..... the first worker in one day zakchanchivat the working plan in 10 hours, another in 15 hours. In how many hours will both workers if they work together perform work?

Speed of work 1 is equal/t1 also the Speed of work of the second x/t2 Working in common x/t1+x/t2=x/t3 t3=t1*t2 / (t1+t2) of =10*15/(10+15)=6 hours =============================
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