Atank can hold up to 500 gallons of water.a gauge reading shows that it is at 80% of its capacity. how many more gallons can it hold

So we start out by finding out what 80% of 500 is by,

500 * .80 = 400

So if 80% is 400 that means that there is still space available for 100 more gallons! 

How the heck did we know that?!? 

simple 500- 400= 100 

So that leaves us knowing that there are 100 gallons left that can be held!! :) 

                            So your answer is 100 gallons!! 

I hope that this helped!

the speed of a race car going 100mph