Working alone at its constant rate, machine A produces k liters of a chemical in 10 minutes. Working alone at its constant rate, machine B produces k liters of the chemical in 15 minutes. How many minutes does it take machines A and B, working simultaneously at their respective constant rates, to produce k liters of the chemical?

___________ minutes
_________________

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For Machine A, in 1 minute it produces K/10 litres.
For Machine B, in 1 minute it produces K/15 litres.
Together in 1 minute they produce k/10 + k/15 litres = k/6 litres
So, K/6 litres are produced in 1 minute.
K litres are produced in 6 minutes.
Ans - 6 minutes.