Question 1046867
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how many pounds of 60-40 solder (60% tin, 40% lead) must be mixed with 40-60 solder to produce 60 grams of 55-45 solder?
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Let x be "how many pounds of 60-40 solder (60% tin, 40% lead) must be mixed".

Then the governing equation is

0.6x + 0.4(60-x) = 0.55*60,  or

0.6x + 24 - 0.4x = 33,  or

0.2x = 33 - 24,

0.2x = 9,

x = {{{9/0.2}}} = 45.

<U>Answer</U>. Mix 45 gram of 60-40 solder with 60-45 = 15 gram of 40-60 solder.

<U>Check by tin</U>.   0.6*45 + 0.4*15 = 33.  0.55*30 = 33.  Correct! 

<U>Check by lead</U>.  0.4*45 + 0.6*15 = 27.  0.55*60 = 27.  Correct! 
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