In a certain factory there are five workers A, B, C, D and E. A can complete a work in 4 minutes, B in 5 minutes, C in 6 minutes, D in 10 minutes and E in 12 minutes. The average number of units of work completed per worker per minute will be

Concept & Strategy Work rate is the reciprocal of the time taken to complete a job. To find the average work done per worker per minute, first determine the individual work done by each worker in one minute, sum them up to find the total team output per minute, and then divide by the total number of workers. $$Rate = \frac{1}{\text{Time taken}}$$ Step-by-Step Solution * Find the individual 1-minute work (units of work completed per minute) for each worker: * A's work in 1 min = $1/4$ * B's work in 1 min = $1/5$ * C's work in 1 min = $1/6$ * D's work in 1 min = $1/10$ * E's work in 1 min = $1/12$ * Calculate total work done by all 5 workers collectively in 1 minute: * Total = $1/4 + 1/5 + 1/6 + 1/10 + 1/12$ * Find the LCM of 4, 5, 6, 10, and 12, which is 60. * Total = $\frac{15 + 12 + 10 + 6 + 5}{60} = \frac{48}{60} = \frac{4}{5} = 0.80$ units of work per minute. * The question specifically asks for the average work per worker per minute. * Average = $\frac{\text{Total Work per Minute}}{\text{Number of Workers}}$ * Average = $\frac{0.80}{5} = 0.16$. Exam Strategy & Shortcut Instead of dealing with fraction additions, assume the total work is the LCM of all the given times (60 units). Calculate efficiencies (units/min): A=15, B=12, C=10, D=6, E=5. Total units completed by all workers in 1 min = 48 units. Average units completed per worker per min = $48 / 5 = 9.6$ units. Since we scaled the total work to 60 units, the fractional part of 1 standard unit of work is $9.6 / 60 = 0.16$. This LCM method safely prevents fractional addition mistakes. Common Pitfall Students often stop calculating after finding the total work per minute (0.80) and immediately select option (c). You must read carefully: the question specifically asks for the average *per worker*, requiring that crucial final division by 5. Final Answer Therefore, the correct answer is 0.16.