Question

If an employee collects sample of water from $45$ houses for checking lead quantity in water. If he starts the first house at $9:00$ AM and starts the sixth house at $10:00$ AM, how many minutes will it take the employee to collect samples from all the houses, assuming it takes the same amount of time at each house?

Answer 1

In $1$ hour he completes $5$ houses or it takes him $1$ hour to complete $5$ houses.

Hence, it takes him exactly $\frac{1}{5}$ hours to complete $1$ house.

Now $1$ hour is $60$ min.

Hence it takes him $12$ minute to complete $1$ house.

Thus, to complete $45$ houses, it will take him $45\times 12=540$min.