# maths

A piece of metal has a volume of 20 cm^3 and a mass of 300g.Calculate the density of the metal in kg/m^3.i got 15.plz confirm my answer.And how does one go about this.2.5 litres of water density 1g/cm^3 is added to 8 litres of alcohol density 0.8 g/cm^3.Calculate the density of the mixtures

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1. well, since density = mass/volume, that gives
300g/20cm^3 = 15 g/cm^3
so you are correct.

for the alcohol mixture, just figure total mass / total volume
2.5L of water = 2500cm^3, so its mass is 2500*1 = 2500g
8L of alcohol = 8000cm^3, so its mass is 8000*0.8 = 6400g
So, the density of the mixture is
(2500+6400)g / (2.5+8)L = 8900g/10.5L = 847.6 g/L = 0.8476 g/cm^3

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2. I need more help to physics as well.
i have exams in 7 days of physics can somene help me?

Q. A footballer has a mass of 72KG. Calculate the wieght of this Footballer.

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3. 72Kg×10Kg/N =720N

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