Bob can cut through a log in two minutes. How long will it take bob to cut a 20-foot log into 2-foot sections?

Question

ehat is the answer of this problem I can't figure it out what are the steps to solving this problem 

Answer 1

You have a log that is 20 feet long, and you are breaking it into 2-foot long sections.

We are cutting it into 10 equal pieces, each piece is 2 feet long (20 feet ÷ 2 feet = 10 pieces)

I am going to make a diagram where an equal sign, =, is a piece of the tree, and a slash, /, is a cut.

 

=/=/=/=/=/=/=/=/=/=

 

If we look at this, there are 10 pieces, and 9 cuts.

"Bob can cut through a log in two minutes."

This means that each of the 9 cuts takes 2 minutes, 9×2=18

It will take Bob 18 minutes to cut up the log.

Answer 2

The problem is tricky because you need to count cuts, not sections. Once you have counted the number of cuts, you just need to multiply by the time per cut to get your answer.  So, how many cuts do you need?

 

Ten pieces, each two feet long, would be a total of 20 feet, which just so happens to be the length of your log.  So, you will need ten cuts (in general), but only nine for this log because the last cut you already got for free from whoever felled the tree.  In other words, once you make the 9^th cut, the left over piece is already two feet, so you don't need to make a 10^th cut.

 

To be more "math-y" about it, the number of cuts, c, is simply the length, l, divided by section length, s, minus one, if there is no remainder.  Examples:

    cuts(20 foot log, 2 foot sections) = 20/2 - 1 (since 20/2 = 10 r. 0) = 9

    cuts(21 foot log, 2 foot sections) = 21/2 - 0 (since 21/2 = 10 r. 1) = 10

 

So the final answer is just 9 * 2 = 18 minutes.