SOLUTION: Dearest tutors, can you help me regarding my problem? thank you for that.. 4. A 30-kilogram bag of cement mix contains 25% and 75% sand. How much pure cement must be added to prod

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Question 49548: Dearest tutors, can you help me regarding my problem? thank you for that..
4. A 30-kilogram bag of cement mix contains 25% and 75% sand. How much pure cement must be added to produce a cement mix that is 40% cement?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A 30-kilogram bag of cement mix contains 25% and 75% sand. How much pure cement must be added to produce a cement mix that is 40% cement?
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Start:
Amount = 30 kg ; amount of cement= 0.25(30)= 7.5 kg
Add:
Amount = x kg ; amount of cement= 100%x = x kg
End up With:
Amount = (30+x) kg amount of cement= 0.40(30+x)= (12+0.4x) kg
EQUATION:
cement + cement = cement
7.5 + x = 12+0.4x
75 + 10x = 120 + 4x
6x=45
x= 7.5 kg ( amount of pure cement that must be added)
Cheers,
Stan H.