
Divide both sides by 7.

n must be less than or equal to 3. n can be 3 or any number under 3.
For example, n can be 1, 2, 3.
The 4 litres of red has to be 2 parts of the mixture, so each part will be 2 litres. Therefore 3 parts of cream will be 6 litres and the one part of blue will be 2 litres.
Answer:
1.60 
Step-by-step explanation:
Assuming that this is a cylindrical pipe, the area can be determined by applying the formula for calculating the area of a circle.
i.e Area = 

So that,
for the inner part of the pipe,
r = 
= 
= 2.5 feet
Area of the inner part of the pipe = 

= 3.14 x 
= 19.625
Are of the inner part of the pipe is 19.63
.
Total diameter of the pipe = 5 + 0.2
= 5.2 feet
r = 
= 2.6 feet
Area of the pipe = 

= 3.14 x 
= 21.2264
Area of the pipe is 21.23
.
Thus the cross sectional area = Area of the pipe - Area of the inner part of the pipe
= 21.2264 - 19.625
= 1.6014
The cross sectional area of the cement pipe is 1.60
.
Answer:
A 5.5% = 5400 B 5% = 1800
Step-by-step explanation:
A + B = 7200
A * 0.055 + B * 0.05 = $387
A = 7200 - B
(7200 - B)*0.055 + B*0.05 = 387
396 - 0.055B + 0.05B = 387
396 - 0.005B = 387
0.005B = 9
B = 1800
A = 7200 - B = 7200 - 1800
A = 5400