A turner can complete an order in 6 hours, and his apprentice in 10 hours. What part of the order will remain unfulfilled

A turner can complete an order in 6 hours, and his apprentice in 10 hours. What part of the order will remain unfulfilled after three hours of working together with the turner and the apprentice?

1. We count as 1 (unit) the entire volume of work.
Labor productivity of a turner (1/6) units / hour.
The productivity of his student (1/10) units / hour.
Let’s find their joint performance.
1/6 + 1/10 = 5/30 + 3/30 = 8/30 = 4/15 units / hour.
2. Let’s determine what part of the order they will complete in 3 hours of joint work.
(4/15) * 3 = 12/15 = 4/5.
3. Determine the part of the outstanding work.
1 – 4/5 = 5/5 – 4/5 = 1/5 = 20/100 = 20%.
Answer: 1/5 part or 20% of the order will remain unfulfilled after 3 hours of teamwork.