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

Answer: b .
`(1)/(3)*12` hours

Explanation:

Given : A oil company fills
`(1)/(12)` of a tank in
`(1)/(3)` hour.

i.e. Time taken to fill
`(1)/(12)` of a tank=
`(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
`(1)/(12)*12` tank=
`(1)/(3)*12` hour.

⇒ Time taken to fill 1 tank=
`(1)/(3)*12=4` hour.

Hence, it will take
`(1)/(3)*12` hours or 4 hours for the tank to fill completely.

Thus , the correct answer is b .
`(1)/(3)*12` hours

Answer 2

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