Two spinning machines A and B can together produce 300000 metres of cloth in 10 hours. If machine B alone can produce the same amount of cloth in 15 hours. Then how much cloth can machine A produce alone in 10 hours ?

Answer: Option B

Length of cloth produced by A and B in 10 hours
$$=300000\text{ metres}$$
Length of cloth produced by B in 10 hours
$$\begin{array}{rl}& =\left(\frac{300000}{15}\times 10\right)\\ & =200000\text{ metres}\end{array}$$
∴ Length of cloth produced by A in 10 hours
$$\begin{array}{rl}& =\left(300000-200000\right)\\ & =100000\text{ metres}\end{array}$$