Question

A chemist mixes a 10% hydrogen peroxide solution with a 25% hydrogen peroxide solution to create 30 liters of a 15% hydrogen peroxide solution. How many liters of the 10% solution did the chemist use to make the 15% solution?

Answer 1

So what does 10% of some solution mean? It means that you take the amount that's in there and divide it by the total volume of other stuff. So like if you have 10% salt solution and let's say it has 20 liters of stuff like salt and water then that means that 2 liters of the 20 liters is salt. So you write this as 2/20=10%.

Try using this to help you figure this out, give it your best shot.

Answer 2

I don't understand

Answer 3

i would approach this with a system of equations ....

Answer 4

A chemist mixes a 10% hydrogen peroxide solution with a 25% hydrogen peroxide solution to create 30 liters of a 15% hydrogen peroxide solution.

let x and y represent the amounts of solution that was used such that:

x+y = 30

now we can focus on the percentages used: if x is 10% and y is 25% then we know that:

.10x + .25y = 30(.15)


this gives us 2 equations in 2 unknowns

Answer 5

ok

Answer 6

so, given:

x + y = 30

.10x + .25y = 30(.15)

what is your favorite method of solving a system of equations?

Answer 7

Multiplication or Addition ?

Answer 8

if you mean elimination .. i know they use different terms for it these days. then we can apply that.

what is your idea to eliminate one of the variables?

Answer 9

You subtract one of them from both sides?

Answer 10

lets say we want to get rid of the x parts; if we multiply the top by say: -.10 and add the results ...

-.10x -.10y = -30(.10)
.10x + .25y = 30(.15)
---------------------
0x + ______________

what is the results?

Answer 11

Do you multiply those?

Answer 12

add (combine) like terms

-.10x + .10x = 0x

what do the y terms get us? the constant terms get us?

Answer 13

-9.75 ?

Answer 14

-.10x -.10y = -30(.10)
.10x + .25y = 30(.15)
---------------------
0x + ______________


soo ...

-.10x+ .10x = 0x

-.10y + .25y = ??

-30(.10) + 30(.15) = ??

Answer 15

if this method is to difficult, we can always try the basic substitution method

Answer 16

-.10y + .25y = 0.15
-30 * .10 = -3 30 * .15 = 4.5

Answer 17

-3 + 4.5 = 1.5 ?

Answer 18

correct so far :)

-.10x -.10y = -30(.10)
.10x + .25y = 30(.15)
---------------------
.15y = 1.5

now we can solve for y

Answer 19

1.5 divided by .15 = 10

Answer 20

so, y=10

and since x + y = 30, what is x?

Answer 21

20 ?

Answer 22

yeah

so we now know what the solution is

x + y = 30
20+10 = 30

.10x + .25y = 30(.15)

20L of 10% and 10L of 25%

Answer 23

So the answer is 20 liters ?

Answer 24

How many liters of the 10% solution did the chemist use to make the 15% solution?

we need both results

Answer 25

Yeah , its 20. Thank you so much

Answer 26

youre welcome :) good luck

Answer 27

just for the record ... @igreen any thoughts?

Answer 28

Looks great!