An engineer wants to make a 60% cement mixture. How many pounds of an 80% cement mixture must she mix with 14 pounds of a 50% mixture to create a 60% cement mixture?
in 14 pounds of a 50% mixture we have 0.5*14=7pounds of cement lets think that we need x pounds of mix of an 80% cement so in that mix we will have 0.8x pounds of cement. If we'll mix both we wiil have (14+x)pounds of mix and we have (0.8x+7) cement on it.
in mixture mix there are 60% of (x+14)pounds of cement so it is 0.6(x+14) of cement
make equation (sum of mix) 0.6(x+14)=0.8x+7 0.6x+8.4=0.8x+7 0.2x=1.4 x=7
Answer: engineer need 7pounds of 80% mix
P.s. look at the picture it more easy for understanding!
