At least how many grams of pure bronze must be alloyed with 387 grams

Question

At least how many grams of pure bronze must be alloyed with 387 grams of pure copper to create an alloy that is no more than 90% copper?

A. 13
B. 43
C. 103
D. 348
E. 430

sillyboy · Answer

B.

387 + 43 = 430

430*.9 = 387. Therefore, Copper is exactly 90%

EgmatQuantExpert · Answer

Hey,

PFB the solution.

Given  :
 • Amount of pure copper =  387  grams.

Find  : 
 • Minimum amount of bronze in grams to be added, which results in copper less than or equal to  90 % in the alloy.

Approach and Working  :

• Let the amount of bronze added be  x  grams.
• Total amount will be the  (Copper + Bronze) = ( 387 + x)  grams.
• Percentage of copper in the alloy  = \frac{387}{(387 + x)}  grams
• As per the given condition –
 o  \frac{387}{(387+x)}  ≤  \frac{90}{100} 
o  387*10  ≤  9x + 387*9 
o  9x  ≥  387 
o  x  ≥  \frac{387}{9} 
o  x  ≥  43 
o Thus, the amount of bronze can be more than  43  grams, to ensure that percentage of copper is less than or equal to  90 % in the alloy.   
• Butwe need to find the minimum amount of bronze needed, therefore,  the least amount of bronze needed would be  43  grams .
• Correct Answer :   Option B

Thanks,
Saquib
Quant Expert
e-GMAT

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raj2812 · Answer

SOLUTION: the question stem means -> 387gms of copper is 90% of the alloy Therefore 387=90/100*ALLOY ALLOY=387*100/90=430GMS BRONZE=430-387=43 ANS B

gracie · Answer

let b=grams of bronze to be added
b=.10(387+b)
b=43
B

akadiyan · Answer

At least how many grams of pure bronze must be alloyed with 387 grams of pure copper to create an alloy that is no more than 90% copper?

387 gram of pure copper should be no more than 90%.

If we consider 387 grams as 90% , then we get 10% as 387/9 = 43. We need 43 grams of pure bronze must be added.

Ans:   B

ScottTargetTestPrep · Answer

We can let n = the number of grams of pure bronze needed and create the equation:

387/(387 + n) = 9/10

3870 = 9(387 + n)

430 = 387 + n

43 = n

Alternate Solution:

We can let x = the total minimum weight of the alloy and create the equation:

0.9x = 387

9x = 3870

x = 3870/9

x = 430

Since the total minimum weight of the alloy must be 430 grams, we see that the minimum amount of bronze must be 430 - 387 = 43 grams.

Answer: B

pulak1988 · Answer

easy.
90% of total is copper which is 387, so total is 430, hence bronze should be 43.
asnwer 'B'

bumpbot · Answer

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At least how many grams of pure bronze must be alloyed with 387 grams

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At least how many grams of pure bronze must be alloyed with 387 grams

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