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If the cost of a certain house in 1983 was 300 percent of its cost in 1970, by what percent did the cost increase ?
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n is the cost in 1970
3n is the cost in 1983
because we compute an increase :
(3n-n)/n = 2n/n=2 *100= 200%
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If machine X can produce 1000 bolts in 4 hours and Machine Y can produce 1000 bolts in 5 hours, how many hours can Machine X and Y, working together at these constant rates, produce 1000 bolts?
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1/4 + 1/5=1/h
5/20+4/20=1/h
9/20=1/h
9h=20
h=20/9=2 2/9
For producing 1000 together they need 2 2/9 hours
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If 6 pounds of nuts that cost 1.20 $ per pound are mixed with 2 pounds of nuts that cost 1.60$ per pound what is the cost per pound of the misture?
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6(1.20)+2(1.60)=10.40
10.4/8=1.30 $
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How many liters of a solution that is 15 % salt must be added to 5 liters of a solution that is 8 percent salt so that the resulting solution is 10 % salt?
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0.15n+0.08(5)=0.10(n+5)
n=2 liters
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