60 because each bag has to be the same
Let's call the number we're looking for . We know that is twice as much as .
Twice as much as a number simply means the double of that number, and in turn the double of a number means to muliply that number by 2.
So, in order to obtain , you have to multply by 2. In formula, you have
or simply
we know there are 5280 feet in 1 mile, and there are 3600 seconds in 1 hour.