Let 
= amount of salt (in pounds) in the tank at time 
(in minutes). Then 
.
Salt flows in at a rate
and flows out at a rate
where 4 quarts = 1 gallon so 13 quarts = 3.25 gallon.
Then the net rate of salt flow is given by the differential equation
which I'll solve with the integrating factor method.
Integrate both sides. By the fundamental theorem of calculus,
After 1 hour = 60 minutes, the tank will contain
pounds of salt.
Answer:the answer is A
Step-by-step explanation:
2x+3=7
2x+3-3=7-3
Whenever moving a number to the other side you have to change the sign .
2x= 4
x=2
Answer:
45 girls
Step-by-step explanation:
- Remark
- There are only 2 choices for gender. So if the class is 60% girls, the there must be 100 - 60 = 40% for the boys.
- But we are told that the boys are 30 in number.
- Let x = the total number of students.
Solution
- 40/100 * x = 30 Change the % to a decimal
- 0.4 x = 30 Divide both sides by 0.4
- 0.4 x / 0.4 = 30 / 0.4 Do the division
- x = 30/0.4
- x = 75 students in total
Formula
Total of Boys and Girls = Number of boys + number of girls.
Givens
- Total = 75
- Number of boys = 30
Solution II
- 75 = x + 30 Subtract 30 from each side
- 75 - 30 = x +30 - 30
- 45 = x
- There are 45 girls in the class.
12 hours..........
+ - = 1
Multiply by 12 to clear the fractions
3t + 2t - 4t = 12
t = 12 hrs to fill the pool
