Question

how many liters each of 15% acid and 33% acid should be mixed to get 120 liters of 21% acid?
by using a system of equation

I get x=80 and y is equal to 40 is this correct?

Answer 1

x + y = 120
.15x + .33y = 120(.21)

x = 80, y = 40
correct

Answer 2

thank you

Answer 3

i have one more for you to look at dealing with another system of equattion

Answer 4

Okay

Answer 5

a freight train and an express train leave towns 390 km apart, traveling toward one another. The freight train travels 30 km per hr slower than the express train. They pass one another 3 hr later. What are their speeds? use a system of equations

Answer 6

should i set it up like 390=x+y/30
390=x-y/3 or should i not do that cause then i would get 71.5 for x and 58.5 for y

Answer 7

so how should i set this one up as a system of equation?

Answer 8

Hang on a minute, sorry

Answer 9

oh okay

Answer 10

We have to use d = rt for this

Answer 11

We're given that the speed of the express train travels 30km faster than the freight train, so
speed of freight train = x
speed of express train = x + 30

The distance the express train travels is only part of the total distance.
The distance the freight train travels will represent the remaining distance.

so let

distance of express = y
distance of freight = 390 - y

Now you can set up the system

Freight Train:
y = 3x

Express Train:
390 - y = 3(x + 30)

Answer 12

So the system to solve is

y = 3x
390 - y = 3(x + 30)

Answer 13

and from there i get 390-y=3x+90 correct?

Answer 14

yes, isolate y in the second equation, then use your graphing calc to figure out the intersection point

Answer 15

then i get 300-y=3x

Answer 16

You should get something like

y = 3x
y = 300 - 3x

Answer 17

Notice now you have two equations which you can graph on your calculator. Or you can just solve manually.

Answer 18

yes

Answer 19

thanks

Answer 20

its not adding up to me

Answer 21

i think i am supposed to get 80 for x

Answer 22

and y should be 50

Answer 23

but the way yo have me doing it gives me 50 for x and 150 for y

Answer 24

on never mind its supposed to add up to 150 correct?

Answer 25

The numbers are correct

Answer 26

okay got it. so i have 50 for x and 150 for y

Answer 27

Do you know what the numbers mean?

Answer 28

x is for the speed of the freight train and y is for the speed expressed by the freight train correct

Answer 29

Yes, what do the numbers 50 and 150 mean?

Answer 30

x= 50 speed of frieght and y=150 spped of expressed by the freight

Answer 31

"expressed by the freight" is not the proper way to describe it. There are two trains: one is a freight train, the other is an express train.

50 km/h is the speed of the freight train
150 is the distance the express train travels

However, you need to find the speed of the express train.