Math Is Fun Forum

So the object of the game is to add 28 to the last person who added 28. it sounds confusing i know. Heres an example:

i say 28.
The first person to comment adds 28 so they would say 56.
now the next person adds 28 to 56 and so on.

i start! 

28!

hi burgess

To do problems like this, vary one thing at a time.

If the number of days is held constant and you reduce the time from 7 to 6 hours, that will need more laborers (as they've got less time).  So multiply by 7/6.

If the number of days is now allowed to change from 18 to 30 days, that will need less laborers (they've got more days).  So multiply by 18/30.

So the number of laborers required will now be:

30 x 7/6 x 18/30 =

Alternatively, invent a unit to describe what has to be done.  Let's call it the person/hour/day unit.

To start with there are 30 x 7 x 18 person/hour/days of work to do.

But they work 6 hours in a day, so 30 x 7 x 18 divided by 6 person/days to complete the job.

But they have 30 days to do it, so (30 x 7 x 18)/6 divided by 30 people will be needed.

As you can see, it comes to the same calculation either way.

Hope that helps, 

Bob

ps.  More on this at http://www.mathsisfun.com/algebra/direc … ional.html