4. The density and strength of concrete are determined by the ratio of cement and aggregate. Suppose that a contractor has 480 cubic feet of a dry concrete mixture that is 70% sand by volume. How much pure sand must be added to form a new mixture that is 75% sand by volume?

Answers

Answer 1
Answer:

Answer:

The answer is 96ft^3

Explanation:

T=initial concrete mixture

S1=initial amount of sand

S2=final amount of sand

T2=final amount concrete mixture

C=amount of cement

Data:

T=480Ft^3

 the quantities of the initial mixture are

S=0.7*480=336Ft^3

C=0.3*480=144 Ft^3

 we pose the following equations

144+S2=T2

T2*0.75=S2  

if we solve

S2=144/(1/0.75-1)=432ft^3

to know how much we should add we subtract it from the initial amount of sand

Answer=432ft^3-336ft^3=96ft^3


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Answers

The mass of the piece of copper is equal to 121.2 g when its specific heat capacity is 0.385 J/g°C.

What is the specific heat capacity?

The specific heat capacity can be described as the amount of heat required to raise the temperature in one kilogram of a substance by one-degree Celcius.

The temperature of the material will change whenever the heat is absorbed or lost by it.

Q = mCΔT

Given, the amount of energy transferred, Q = 3500 J

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The specific heat capacity of the copper, C = 0.385 J/g°C

The mass of the piece of copper for the given change in temperatures can be calculated as:

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m = 121.2 g

Therefore, the mass of the piece of copper is equal to 121.2 g.

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