# Video: AF5P2-Q25-318131028637

Density = mass/volume. Work out the mass when the density is 3 g/cm³ and the volume is 4 cm³. Circle your answer. 0.75 g, 12 g, 1 1/3 g, 24 g.

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### Video Transcript

Density equals mass over volume. Work out the mass when the density is three grams per centimetre cubed and the volume is four centimetre cubed. Circle your answer. The options are 0.75 grams, 12 grams, one and a third grams and 24 grams.

Well, the first thing we want to do is take a look at the question. And the question says that we want to work out the mass. But we’ve got a formula that tells us the density, so we’re gonna need to rearrange our formula to help us find out what the mass is going to be.

So, if we have density equals mass over volume, and we want mass to be the subject of formula, then what we need to do is remove volume from the denominator. And to do that, we multiply each side of our formula by volume. So therefore, when we do that, we get density multiplied by volume is equal to the mass. So, we now have a formula for the mass.

We could also work it out using the mass-density-volume triangle. And with this, what we do is you cover up the one that you’re looking for and you see what’s left. So, if we’re trying to find out the formula for mass, we cover mass up. And we’re left with D and V. And because D and V are next to each other, this means multiplied by. So therefore, we could say that mass is equal to density multiplied by volume.

Okay, great, now, let’s use this to solve the problem. Well, we know that the density is equal to three grams per centimetres cubed. And we know that the volume is equal to four centimetres cubed. So, now, what we need to do is multiply these together. So therefore, the mass is gonna be equal to three multiplied by four, which gives us a final answer of 12. So therefore, we can say that the second answer must be the correct answer. And that the mass, when the density is three grams per centimetre cubed and the volume is four centimetres cubed, is 12 grams.