During a certain month, 40 percent of all the oil used by a certain fa

Question

During a certain month, 40 percent of all the oil used by a certain factory was used by the oil heater. The cost per gallon of the oil used by the oil heater was half the cost per gallon of the rest of the oil used by the factory. For that month, the cost of the oil used by the oil heater was what fraction of the cost of all the oil used by the factory?

A. $\frac{1}{6}$

B. $\frac{1}{5}$

C. $\frac{1}{4}$

D. $\frac{1}{3}$

E. $\frac{1}{2}$

A.  \frac{1}{6}

B.  \frac{1}{5}

C.  \frac{1}{4}

D.  \frac{1}{3}

E.  \frac{1}{2}

gmatophobia · Accepted Answer

During a certain month, 40 percent of all the oil used by a certain factory was used by the oil heater.

Assume in that given month 100 gallon of oil was used.

Oil used by Oil Heaters = 40 gallons 
 Oil used by Other Heaters = 60 gallons

The cost per gallon of the oil used by the oil heater was half the cost per gallon of the rest of the oil used by the factory.

Assume

Cost of per gallon oil used by Oil Heaters = $1 
 Cost of per gallon used by other Heaters = $2

For that month, the cost of the oil used by the oil heater was what fraction of the cost of all the oil used by the factory?

Cost of Oil used by Oil Heaters = 40 * $1 = $40 
 Cost of Oil used by Other Heaters = 60 * $2 = $120

Required Ratio =  \frac{40}{40+120} = \frac{40}{160} = \frac{1}{4}

Option C

saynchalk · Answer

Let total Oil used be 100, and cost per unit of oil be $1

Cost for Oil heater = 40 * 1/2 = $20
Cost used by other equipment = 60 * 1 = $60

Ratio of costs is 20:60

Fraction of the cost of Oil heater's usage of oil = 20/80
Simplify this to get = 1/4

Manifesting710 · Answer

let A = total oil

so oil used by oil heater = 0.4A
 
\frac{Total cost of Oil used by oil heater}{0.4A} = \frac{1}{2}*\frac{total remaining oil cost}{ 0.6A}

Cost Oil heater = \frac{1}{3}* Cost Remaining

or 3*(C0st Oil Heater) = 1 * Cost Remaining

\frac{Cost Oil}{Total Cost} = \frac{cost Oil }{ cost oil + cost remaining} 
= \frac{1}{4}

Is my approach correct? or did i get lucky?  Bunuel   gmatophobia  someone tell

MartyMurray · Answer

Your approach is logically sound.

MartyMurray · Answer

During a certain month, 40 percent of all the oil used by a certain factory was used by the oil heater. The cost per gallon of the oil used by the oil heater was half the cost per gallon of the rest of the oil used by the factory. For that month, the cost of the oil used by the oil heater was what fraction of the cost of all the oil used by the factory?

A. $\frac{1}{6}$

B. $\frac{1}{5}$

C. $\frac{1}{4}$

D. $\frac{1}{3}$

E. $\frac{1}{2}$

Let P be the cost per gallon for the rest of the factory.

Let T be the total number of gallons used.

So, the fraction we are looking for is the following:

\frac{{.40(T)(.5P)}}{{.40(T)(.5P) + .60(T)(P)}}

The Ts and Ps cancel out.

\frac{.2}{.2 + .60}

\frac{1}{4}

A.  \frac{1}{6}

B.  \frac{1}{5}

C.  \frac{1}{4}

D.  \frac{1}{3}

E.  \frac{1}{2}

Correct answer:  C

hemanthPA · Answer

Consider total qty of oil used is 100L

Given: oil heater uses 40L of oil, and cost comp
 
Oil - QTY - Cost
X - 40L - X/2 $/g
Y – 60L - X $/g

Ratio of $ of oil used by the oil heater was what fraction of the cost of oil used by the factory

i.e., (40*x/2)/((60*x)+(40*x/2)) = 20x/80x = 1/4

RobertVericPrep · Answer

When you read this question, first think "part over whole". i.e. Part/Whole.

When you see a percent question you often want to pick 100 for the total, i.e. the "whole". The parts are 40 units used by the oil heaters and the 60 units that are used elsewhere.

But are those the "parts" and the "whole" we need to know to answer the question? Actually, no.

The Part/Whole we need to figure out is (COST of oil used by heaters) / (COST of all oil)

Let's say the 60 units of oil used elsewhere costs $1/unit, i.e. $60. Then the 40 units used by the oil heaters would cost only 50 cents per unit, i.e. $20. So 20 and 60 are the parts we care about.

What about the whole? The whole is (COST of all oil), which is 20 + 60, which equals 80.

So (COST of oil used by heaters) / (COST of all oil) = 20 / (20 + 60) = 20/80 = 1/4

Answer C

During a certain month, 40 percent of all the oil used by a certain fa

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During a certain month, 40 percent of all the oil used by a certain fa

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