Need a little help with this ratio question

  • Thread starter tehmatriks
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  • #1
tehmatriks
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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


Homework Equations





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
 

Answers and Replies

  • #2
berkeman
Mentor
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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


Homework Equations





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% ?
 
  • #3
36,322
8,285
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.
 
  • #4
accystan
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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?
 
  • #5
36,322
8,285
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.
 
  • #6
accystan
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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.
 
  • #7
eumyang
Homework Helper
1,347
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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.
 
  • #8
VietDao29
Homework Helper
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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?
 

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