Let 
be the number of liters of the 10% solution to be used, and 
the number of liters of the 4% solution. The chemist wants to end up with a 4 liter solution, so
For each liter used in the mixture, a concentration of either 10% or 4% acid will be contributed, and the goal is to make a 4L solution whose concentration is 7%, which means
Solving for 
gives 
, so 2L of both solutions is needed.
The answer to this question is Letter B.
Answer:
C = 28.26 in
Step-by-step explanation:
the circumference (C) is calculated as
C = πd ( d is the diameter ) , then
C = 3.14 × 9 = 28.26 in
No it doesn’t not represent a function
Answer:
217.04 cm²
Step-by-step explanation:
We should first calculate the area of the rectangle:
A= 14*21 =294cm²
then we should substract the area of the half-cercle :
A'= (7²*π)/2=76.96 cm²
then the area of the shaded area is :
A"= 294-76.96= 217.04 cm²
