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# A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and

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Math Expert
Joined: 02 Sep 2009
Posts: 60644
A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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03 Jul 2015, 03:57
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Difficulty:

55% (hard)

Question Stats:

68% (02:07) correct 32% (02:23) wrong based on 293 sessions

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A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and 75% Brent Crude Oil. 2/3 rd of the remainder of the tank is filled with 400 barrels of WTI Crude Oil. How much WTI Crude Oil is in the tank?

A. 425 barrels
B. 437.5 barrels
C. 450 barrels
D. 500 barrels
E. 650 barrels

Kudos for a correct solution.

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Math Expert
Joined: 02 Sep 2009
Posts: 60644
Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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03 Jul 2015, 07:37
2
Bunuel wrote:
A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and 75% Brent Crude Oil. 2/3 rd of the remainder of the tank is filled with 400 barrels of WTI Crude Oil. How much WTI Crude Oil is in the tank?

A. 425 barrels
B. 1300/3 barrels
C. 450 barrels
D. 500 barrels
E. 600 barrels

Kudos for a correct solution.

Sorry guys, there was a typo it's "2/3 rd" not 3/4.
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Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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03 Jul 2015, 07:57
2
Bunuel wrote:
A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and 75% Brent Crude Oil. 2/3 rd of the remainder of the tank is filled with 400 barrels of WTI Crude Oil. How much WTI Crude Oil is in the tank?

A. 425 barrels
B. 437.5 barrels
C. 450 barrels
D. 500 barrels
E. 650 barrels

Kudos for a correct solution.

Let the total volume of the tank be T ($$unit^3$$)

Oil in the tank =0.25T

WTI in the 0.25T of oil = 0.25T*0.25=T/16

Now the remainder of the tank = 3T/4 (as 0.25T is with mixture of oils while 0.75 or 3/4 of the tank is only with WTI) has 2/3rds with 400 barrels of WTI

Thus, 2/3*0.75T=T/2=400 barrels

Thus, T=800 barrels and WTI = 400+T/16 = 400+800/16 = 400+50=450 barrels., Choice C is the correct answer.
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Joined: 02 Aug 2009
Posts: 8336
Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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03 Jul 2015, 07:59
2
Bunuel wrote:
A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and 75% Brent Crude Oil. 2/3 rd of the remainder of the tank is filled with 400 barrels of WTI Crude Oil. How much WTI Crude Oil is in the tank?

A. 425 barrels
B. 437.5 barrels
C. 450 barrels
D. 500 barrels
E. 650 barrels

Kudos for a correct solution.

capacity=x.. 2/3*(3/4)*x=400..x=800..
WTI = 400+ 800/4*4=450
ans C
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Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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03 Jul 2015, 08:53
1
So, calculate the total amount of oil in the tank, from the knowledge that 400 barrels were added.
$$\frac{3}{4}*\frac{2}{3}$$ = $$\frac{400}{x}$$
$$x = 800$$

Then, calculate the number of WTI before 400 barrels were added, making it $$y$$ to keep my algebra organized.
$$1/4$$*$$1/4$$=$$\frac{y}{800}$$
$$y = 50$$

$$x + y = 400 + 50 = 450$$

Alternatively, if the tank is 800 barrels of oil, then 25% of that is 200, and thefore 25% of that is 50. Thus, 400+50 = 450. A,B, and D are out since there is no 5 in the tens digit.

Thanks,
Math Expert
Joined: 02 Sep 2009
Posts: 60644
Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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20 Jul 2015, 05:24
Bunuel wrote:
A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and 75% Brent Crude Oil. 2/3 rd of the remainder of the tank is filled with 400 barrels of WTI Crude Oil. How much WTI Crude Oil is in the tank?

A. 425 barrels
B. 437.5 barrels
C. 450 barrels
D. 500 barrels
E. 650 barrels

Kudos for a correct solution.

OFFICIAL SOLUTION:

The tank was 25% full. Then, 2/3 rd of the remainder of the tank, so 2/3 rd of 75% of the tank, was filled with 400 barrels of WTI Crude Oil. 2/3 rd of 75% is 50%, thus we are told that 50% of the tank amounts for 400 barrels, which makes the capacity of the tank 800 barrels.

Therefore, initially, the tank had $$0.25*0.25*800=50$$ barrels of WTI Crude Oil. After 400 barrels of WTI Crude Oil were added the amount of WTI Crude Oil became $$50 + 400 = 450$$ barrels.

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Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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20 Jul 2015, 14:00
Find the size of the tank, T: The tank starts at 25% full, or 75% empty. 2/3 of the empty portion is 400 Barrels. (2/3 * 3/4)T = 400 --> T=800

Initial WTI amount: 1/4 of tank was initially full with a mixture of 1/4 WTI. 1/4 full * 1/4 mixture * 800 Barrels = 50 Barrels of WTI

50 Barrels + 400 Barrels that were added, gives us a total of 450 Barrels, Answer is C.
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Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and  [#permalink]

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05 Aug 2019, 21:51
We are asked to determine how much WTI is in the tank.

2/3 of the remaining (3/4 is remaining- see highlighted part of tank) is filled with 400 barrels

2/3*3/4= 1/2 of the remaining tank = 400 barrels

So the tank's capacity is 800 barrels

We know 25% of the tank has oil in it comprised of 25% WTI and 75% Brent.
So 1/4*800
= 200 *1/4 = 50 contained within the 25% component

So 400 WTI (in remaining component of tank) + 50 in 25% component = 450
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Re: A tank is 25% full of oil. The oil consists of 25% WTI Crude Oil and   [#permalink] 05 Aug 2019, 21:51
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