if 3 cooks take 11/2 hours to make 15 pizza's how long would it take 6
cooks to make 20 pizza's?

OK let me see if I can work this out (I really used to hate these
bloody type of problems at school)


Anyway here goes

3 cooks take 11/2 hours to make 15 pizza's how long would it take 6
cooks to make 20 pizza's?

6 cooks take 11/4 hours to make 15 pizza's 

6 cooks take 11/12 hours to make 5 pizza's 

6 cooks take 4 times 11/12 hours to make 20 pizza's 

4*11/12 hours = 60*4*11/12 minutes = 220 minutes (3 hours 40 minutes)

Yours Truly 

Mongolia

Er, Mongolia, I think 11/2 is actually 1 and 1/2 or 1.5, not eleven-halves.

Now if it IS eleven halves, your math is spot on.

But if it is 1.5 hours for 3 cooks to make 15 pizzas, then 6 cooks
make 20 pizzas like so:

First, divide both sides by 3, not including the cooks (common factor)
3 cooks make 15/3 pizzas in 90/3 minutes, or 3 cooks make 5 pizzas in 30 minutes.

Now multiply the whole equation (including cooks) by 2.
6 cooks make ten pizzas in 30 minutes

Now multiply by two, but not including the cooks.
6 cooks make 20 pizzas in 60 minutes.

If you prefer, after the first step you can calculate down farther and work up:
3 cooks make 5 pizzas in 30 minutes, then 3 cooks make one pizza every 6 minutes.

Thus, 6 cooks would make one pizza every 3 minutes.

To make 20 pizzas, multiply by 20 (duh) and you get 60 minutes.

Markvmd

I suspect the questioner did in fact mean 1 and 1/2 hours (or 1.5
hours) rather than 5.5 hours as the answer came out to a nice even 1
hour.

However I can only go by what the questioner asked. As Peter O'Toole once
so eloquently put it (in the "Last Emperor") "You must say what you
mean and mean what you say".

Perhaps the questioner can clarify :-).

Kind  Regards

Mongolia