A patient is given exactly 750 millimeters of a mixture of two medications daily. Medication A contains 40% painkiller and medication B contains 20% painkiller. If the patient receives exactly 215 millimeters of painkiller daily, how many millimeters of medication B are in the mixture?
A. 150
B. 225
C. 325
D. 425
E. 550
The OA is D.
Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer. I need your help. Thanks.
A patient is given exactly 750 millimeters of a mixture of
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- ErikaPrepScholar
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When we have a mixtures problem like this, building equations is a great route.
Total volume of medication: a + b = 750
Total volume of painkiller: 0.4a + 0.2b = 215
Isolate a in the first equation:
a = 750 - b
Plug into second equation and solve for b:
0.4(750 - b) + 0.2b = 215
300 - 0.4b + 0.2b = 215
85 = 0.2b
425 = b
So there are 425mls of medication B, or answer choice D.
We could also approach this as a weighted average problem. 215 mls of painkiller is 28.6666% of the 750mls of medication received. This is between 20% concentration (medication B) and 40% concentration (medication A), but slightly closer to 20% concentration. This means that there should be slightly more of medication B (20%) than medication A (40%). Half of 750 is 375, so we want our volume of B to be somewhat larger than that. This rules out all answer options but D and E. From there, we can plug in our remaining answers to see which one gets us the correct volume of painkiller.
Total volume of medication: a + b = 750
Total volume of painkiller: 0.4a + 0.2b = 215
Isolate a in the first equation:
a = 750 - b
Plug into second equation and solve for b:
0.4(750 - b) + 0.2b = 215
300 - 0.4b + 0.2b = 215
85 = 0.2b
425 = b
So there are 425mls of medication B, or answer choice D.
We could also approach this as a weighted average problem. 215 mls of painkiller is 28.6666% of the 750mls of medication received. This is between 20% concentration (medication B) and 40% concentration (medication A), but slightly closer to 20% concentration. This means that there should be slightly more of medication B (20%) than medication A (40%). Half of 750 is 375, so we want our volume of B to be somewhat larger than that. This rules out all answer options but D and E. From there, we can plug in our remaining answers to see which one gets us the correct volume of painkiller.
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- Scott@TargetTestPrep
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We can let a = the amount of medication A and b = the amount of medication B and create the equations:swerve wrote:A patient is given exactly 750 millimeters of a mixture of two medications daily. Medication A contains 40% painkiller and medication B contains 20% painkiller. If the patient receives exactly 215 millimeters of painkiller daily, how many millimeters of medication B are in the mixture?
A. 150
B. 225
C. 325
D. 425
E. 550
a + b = 750
a = 750 - b
and
0.4a + 0.2b = 215
4a + 2b = 2150
2a + b = 1,075
Substituting, we have:
2(750 - b) + b = 1075
1500 - 2b + b = 1075
1500 - b = 1075
425 = b
Answer: D
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We can PLUG IN THE ANSWERS, which represent the amount of Medication B in the mixture.swerve wrote:A patient is given exactly 750 millimeters of a mixture of two medications daily. Medication A contains 40% painkiller and medication B contains 20% painkiller. If the patient receives exactly 215 millimeters of painkiller daily, how many millimeters of medication B are in the mixture?
A. 150
B. 225
C. 325
D. 425
E. 550
When the correct answer is plugged in, the amount of painkiller = 215.
D: Medication B=425, implying that Medication A = 750-425 = 325
Amount of painkiller = (20% of B) + (40% of A) = 85 + 130 = 215.
Success!
The correct answer is D.
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My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
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