Don't let fractions fool you.
[tex] \frac{1}{12} [/tex] of a tank inΒ [tex] \frac{1}{3} [/tex] an hour is equal to:
1/12 of a tank in 20 minutes.
Thus we know in an hour, an oil company can fill 3/12 of a tank (60 minutes in an hour).
3 x 4 = 12, and 12/12 = 1(a whole tank), so we multiply 1 (hour) by 4.
Our answer is that it takes 4 hours to fill a tank.
