Answer:
The chemist needs to add 400mL of 40% solution.
Step-by-step explanation:
The equation

gives the percent concentration
of the final mixture, when
mL of the 40% solution are added.
Now we are asked, how many milliliters
of the 40% solution should the chemist add to get final percent concentration
; this is just a matter of solving the equation

and we solve it the following way:

Thus, the chemist needs 400mL of 40% solution to get 30% concentration of the final mixture.
Answer:
Thousands, probably millions
Step-by-step explanation:
Answer:
7
Step-by-step explanation:
7 is a common positive factor if 14 and 21. 2:3
36 ×

Since 9 is a factor of 36 you can reduce the 36 to 4 and the 9 to one
Then just multiply what is left
4 <span>× 2 = 8
So, Mark completed 8 passes.</span>
Answer:

Step-by-step explanation:
we have the options

the one that is a perfect equare tinomial is:

because we can rewrite this as follows:
this is because we know that

thus

and the other options cannot be represented as a perfect square trinomial, so the correct answer is:
