# Need a little help with this ratio question

## Homework Statement

A tank was 3/4 full of oil. 100 litres of oil were then used. If it was then 2/3 full, how many litres does the tank hold when full

## The Attempt at a Solution

umm, im not even sure how to get started, i know that 3/4 = 75% and 2/3 = 66.6%
but can't quite wrap my head around it. so yea, i need some help, thanks in advance

berkeman
Mentor

## Homework Statement

A tank was 3/4 full of oil. 100 litres of oil were then used. If it was then 2/3 full, how many litres does the tank hold when full

## The Attempt at a Solution

umm, im not even sure how to get started, i know that 3/4 = 75% and 2/3 = 66.6%
but can't quite wrap my head around it. so yea, i need some help, thanks in advance

If 0.1 liters is the difference between those two fractions, how much is 100% ?

Mark44
Mentor
Let x = the number of liters in a full tank.

Now convert these sentences into one equation.
A tank was 3/4 full of oil. 100 litres of oil were then used. It was then 2/3 full.

Hi:

The difference between a tank that is 3/4 full and a tank that is 2/3 full is 100 litres. The word "difference" implies 'subtract'. So if (3/4 - 2/3) = 100l, what is the volume of the whole tank?

Mark44
Mentor
Hi:

The difference between a tank that is 3/4 full and a tank that is 2/3 full is 100 litres. The word "difference" implies 'subtract'. So if (3/4 - 2/3) = 100l, what is the volume of the whole tank?
As stated, this isn't much help. Your equation above says that 3/4 - 2/3 = 100L, which isn't true.

As stated, this isn't much help. Your equation above says that 3/4 - 2/3 = 100L, which isn't true.

I'm not sure why you're saying this is not true. Can you explain why?

Continuing......

If 3/4 - 2/3 = 100 l.

then 1/12 = 100 l.

and tank capacity is 1200 l.

eumyang
Homework Helper
I'm not sure why you're saying this is not true. Can you explain why?

Continuing......

If 3/4 - 2/3 = 100 l.

then 1/12 = 100 l.

and tank capacity is 1200 l.

Since when does the number 1/12 equal 100? That is what you are saying. I know what you are thinking, and I suspect Mark44 does too, but you are missing a crucial piece in your "equation."

And by the way, you're not supposed to post solutions here.

VietDao29
Homework Helper
I'm not sure why you're saying this is not true. Can you explain why?

Continuing......

If 3/4 - 2/3 = 100 l.

then 1/12 = 100 l.

and tank capacity is 1200 l.

Now that you've shown complete solution to the OP...

What Mark44 is trying to say is that: "1/12 = 100l" is not a valid statement. 1/12 is a real number, how can it equal to 100l? 1/12 of what?