How many pounds of an $83 per pound substance must be mixed with an $11 per pound substance to get 240 lbs of an alloy which will cost $28 per pound? Round to the nearest pound.
57 lbs
183 lbs
205 lbs
35 lbs

Question

How many pounds of an $83 per pound substance must be mixed with an $11 per pound substance to get 240 lbs of an alloy which will cost $28 per pound? Round to the nearest pound.  
    57 lbs  
   183 lbs  
   205 lbs  
   35 lbs

anonymous · Answer

make a chart

anonymous · Answer

You can first find the % of each substance needed expressed as a decimal. The amount of the first substance can be x. The amount of the other substance then will be 1-x. Set up an equation as follows:

83x+11(1-x)=28
83x+11-11x=28
72x=17
x=17/72 which is about 0.24

In other words, you need about 24% of the first substance.

0.24*240=57.6, so the closest answer you have is 57 lbs.

Cheers!