Question

An oil company fills 1/12 of a tank in 1/3 hour. At this rate, which expression can be used to determine how long will it take for the tank to fill completely?
a. 1/12 x 3 hours
b. 1/3 x 12 hours
c. 1/3 x 1/12 hour
d. 3 x 12 hours

Answer 1

Selection B is appropriate.

_____
It takes 12 times as long to fill the whole tank as it does to fill 1/12 of the tank.
.. 12 * (1/3 hour) = (1/3)*12 hour

Answer 2

Answer: b . $\dfrac{1}{3}\times12$ hours

Step-by-step explanation:

Given : A oil company fills $\dfrac{1}{12}$ of a tank in $\dfrac{1}{3}$ hour.

i.e. Time taken to fill $\dfrac{1}{12}$ of a tank=  $\dfrac{1}{3}$ hour.

By using the Unitary method, we multiply 12 on bith the sides of the above expression we get

Time taken to fill $\dfrac{1}{12}\times12$  tank=  $\dfrac{1}{3}\times12$ hour.

⇒ Time taken to fill 1 tank=  $\dfrac{1}{3}\times12=4$ hour.

Hence, it will take $\dfrac{1}{3}\times12$ hours or 4 hours for the tank to fill completely.

Thus , the correct answer is b . $\dfrac{1}{3}\times12$ hours