Question

It takes an apprentice twice as long as the experienced plumber to replace the pipes. if it takes them 5 hours when they work together. How long it would take the apprentice alone?

I know the answer is "15 hr" from the book BUT I don't know how to show the work so please help me. Thank you.

Answer 1

It will take the apprentice 15 hours to replace the pipes

Explanation:

1. Let's review the information given to us to answer the question correctly:

Experience of the apprentice = 1

Experience of the plumber = 2

Time it takes to finish the work together = 5 hours

Time it takes the apprentice to finish the work = x hours

2. How long it would take the apprentice alone?

For answering the question. we will use the Inverse Rule of Three, this way:

The more experience a plumber has, the less time it will take her or him to finish the work.

Experience Time

3 = 2 + 1 (Apprentice and plumber working together) 5 hours

1 (Only the apprentice working) x hours

x = 5 * 3 (It's an inverse rule of three, not a direct rule of three)

x = 15 hours

It will take the apprentice 15 hours to replace the pipes