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# Density Maths Question watch

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1. Hi, I've been trying to do this question for ages, please could someone help and explain it to me? Thanks.

Liquid A has a density of 0.7g/cm3
Liquid B has a density of 1.6g/cm3
140g of Liquid A and 128g of liquid B are mixed to make Liquid C
Work out the density of Liquid C.
2. A key thing to remember here is the formula: Density = Mass/Volume (it tells you in the unit! g/cm3)

In the question, you are given the masses of both Liquid A and Liquid B which are mixed (added) to make Liquid C. So from that, you can work out the mass of liquid C, i.e. 140g + 128g = 268g

You need to work out the density of C, and you have the mass already. So what you need to do is find the volume of C...
Once again it is important to recognise that A and B are mixed, so their volumes are added.

The thing to do here is find the volume of A. This can be done because you have been given the mass of A, 140g and it's density, 0.7g/cm3.
Substitute these values into the formula D=M/V
So 0.7 = 140 / V
rearranging gives you
140/0.7 = V
thus 200 = V
so the volume of A is 200 cm3

do the same for b...
1.6 =128 / V
128/1.6 = V
V = 80
so the volume of B is 80 cm3

Remember, A and B are mixed so their volumes are added -> so 200cm3 of A + 80cm3 of B = 280cm3 of C
So the volume of C is 280cm3

We worked out the mass of Liquid C at the beginning, 268g.
So you know the both the mas and volume of Liquid C. What's left?
You guessed it, back into the formula

D = M/V
D= 268/280
D = 0.9571428571428571428...

which should be rounded to something cleaner,
e.g. rounded to 0.96g/cm3
3. [QUOTE=Gabzinc;69374390]A key thing to remember here is the formula: Density = Mass/Volume (it tells you in the unit! g/cm3)

In the question, you are given the masses of both Liquid A and Liquid B which are mixed (added) to make Liquid C. So from that, you can work out the mass of liquid C, i.e. 140g + 128g = 268g

You need to work out the density of C, and you have the mass already. So what you need to do is find the volume of C...
Once again it is important to recognise that A and B are mixed, so their volumes are added.

The thing to do here is find the volume of A. This can be done because you have been given the mass of A, 140g and it's density, 0.7g/cm3.
Substitute these values into the formula D=M/V
So 0.7 = 140 / V
rearranging gives you
140/0.7 = V
thus 200 = V
so the volume of A is 200 cm3

do the same for b...
1.6 =128 / V
128/1.6 = V
V = 80
so the volume of B is 80 cm3

Remember, A and B are mixed so their volumes are added -> so 200cm3 of A + 80cm3 of B = 280cm3 of C
So the volume of C is 280cm3

We worked out the mass of Liquid C at the beginning, 268g.
So you know the both the mas and volume of Liquid C. What's left?
You guessed it, back into the formula

D = M/V
D= 268/280
D = 0.9571428571428571428...

which should be rounded to something cleaner,
e.g. rounded to 0.96g/cm3[/QUOTE
Thank you soooo much! I completely understand it now
4. [QUOTE=Georgie2412;69374548]
(Original post by Gabzinc)
A key thing to remember here is the formula: Density = Mass/Volume (it tells you in the unit! g/cm3)

In the question, you are given the masses of both Liquid A and Liquid B which are mixed (added) to make Liquid C. So from that, you can work out the mass of liquid C, i.e. 140g + 128g = 268g

You need to work out the density of C, and you have the mass already. So what you need to do is find the volume of C...
Once again it is important to recognise that A and B are mixed, so their volumes are added.

The thing to do here is find the volume of A. This can be done because you have been given the mass of A, 140g and it's density, 0.7g/cm3.
Substitute these values into the formula D=M/V
So 0.7 = 140 / V
rearranging gives you
140/0.7 = V
thus 200 = V
so the volume of A is 200 cm3

do the same for b...
1.6 =128 / V
128/1.6 = V
V = 80
so the volume of B is 80 cm3

Remember, A and B are mixed so their volumes are added -> so 200cm3 of A + 80cm3 of B = 280cm3 of C
So the volume of C is 280cm3

We worked out the mass of Liquid C at the beginning, 268g.
So you know the both the mas and volume of Liquid C. What's left?
You guessed it, back into the formula

D = M/V
D= 268/280
D = 0.9571428571428571428...

which should be rounded to something cleaner,
e.g. rounded to 0.96g/cm3[/QUOTE
Thank you soooo much! I completely understand it now
I'm happy to help
5. (Original post by Georgie2412)
Hi, I've been trying to do this question for ages, please could someone help and explain it to me? Thanks.

Liquid A has a density of 0.7g/cm3
Liquid B has a density of 1.6g/cm3
140g of Liquid A and 128g of liquid B are mixed to make Liquid C
Work out the density of Liquid C.
I remember doing this question. Was this in the 2016 maths edexcel paper?

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