A truck's gas tank holds 50 gallons of gas. if one gallon takes 30 seconds to pump, how many minutes will it take to fill the empty tank?

To find how long it will take to fill the tank, you can use the idea that every 30 seconds will get you one gallon closer to being full.

This means to fill 50 gallons, you will need 50 groups of 30 seconds.  

50 x 30 = 1500 seconds

1500/60 = 25 minutes.

It will take 25 minutes.  

You could also think of it as filling 2 gallons every minute.  It would take 25 of these.