Thread: Finding the capacity

Two oil tanks,X and Y, have the same capacity. The amount of oil in tank X is 1/2 of its capacity, and the amount of oil in tank Y is 1200 gallons less than its capacity. If there are 7800 gallons of oil in the two tanks combined, what is the capacity, in gallons, of tank X?

How is it 6000?

Originally Posted by donnagirl

Two oil tanks,X and Y, have the same capacity. The amount of oil in tank X is 1/2 of its capacity, and the amount of oil in tank Y is 1200 gallons less than its capacity. If there are 7800 gallons of oil in the two tanks combined, what is the capacity, in gallons, of tank X? How is it 6000?

Can you solve

I set it up this way:
C1 is the capacity of X.
C2 is the capacity of Y.
0.5*C1 = C2 - 1200
C1 + C2 = 7800
But when I substitute I get a positive 1200 instead of negative.

C1 + 0.5C1 + 1200 = 7800

Originally Posted by donnagirl

I set it up this way:
C1 is the capacity of X.
C2 is the capacity of Y.
0.5*C1 = C2 - 1200
C1 + C2 = 7800
But when I substitute I get a positive 1200 instead of negative.
C1 + 0.5C1 + 1200 = 7800

That setup is simply wrong.
If you solve , you will get .

How can I deduce the right setup (to show where your equation comes from).

Hello, donnagirl!

Two oil tanks, X and Y, have the same capacity.
The amount of oil in tank X is 1/2 of its capacity,
and the amount of oil in tank Y is 1200 gallons less than its capacity.
If there are 7800 gallons of oil in the two tanks combined,
what is the capacity, in gallons, of tank X?

How is it 6000?

. .

Originally Posted by Soroban

Hello, donnagirl!



. .

How is that different from reply #2?

He didn't say it was different; he simply explained HOW (which you didn't do).

Can somebody kick this Thompson guy outta here? Keeps doing this to post his link!
Tired of getting emails due to his posts...