I think you need to make the 6 positive and then add it to 13 which would give you a=19
Assume that the amount needed from the 5% solution is x and that the amount needed from the 65% solution is y.
We are given that, the final solution should be 42 ml, this means that:
x + y = 42 ...........> equation I
This can also be written as:
x = 42-y .......> equation II
We are also given that the final concentration should be 45%, this means that:
5% x + 65% y = 45% (x+y)
0.05x + 0.65y = 0.45(x+y)
We have x+y = 42 from equation I, therefore:
0.05x + 0.65y = 0.45(42)
0.05x + 0.65y = 18.9 .........> equation III
Substitute with equation II in equation III as follows:
0.05x + 0.65y = 18.9
0.05(42-y) + 0.65y = 18.9
2.1 - 0.05y + 0.65y = 18.9
0.6y = 18.9 - 2.1
0.6y = 16.8
y = 28 ml
Substitute with y in equation II to get x as follows:
x = 42-y
x = 42 - 28
x = 14 ml
Based on the above calculations:
amount of 5% solution = x = 14 ml
amount of 65% solution = y = 28 ml
The correct choice is:
The teacher will need 14 mL of the 5% solution and 28 mL of the 65% solution.
Answer:
21
Step-by-step explanation:
Answer:
See below.
Step-by-step explanation:
Addition: closed
Example: -5 + 10 = 5, and -5, 10, and 5 are all integers
Subtraction: closed
Example: 10 - 8 = 2, and 10, 8, and 2 are all integers
Multiplication: closed
Example: -4 * 7 = -28, and -4, -7 and -28 are all integers
Division: not closed
Example: 5/2 = 2.5, and 2.5 is not an integer, although 2 and 5 are integers
The set of integers is closed under addition, subtraction, and multiplication because any addition, subtraction, or multiplication of integers always results in an integer.
The set of integers is not closed under division because a division of integers does not always result in an integer.
You can set this up as a system of equations.
x + y = 19
10x + 25y = 3.70
Your answer would be 31.42 dimes and -12.42 quarters.
