Multiplying mass as kg and grams= 2 different results?

[christian0710]

Hi, I'm just wondering. If you mulitiply 1kg with 0.5kg you get 0.5kg

But if you do the multiplication in grams you get
1000g *500g = 500.000g = 500kg. a dompletely different result.

Why is that? How do you avoid this problem?

 

[e.bar.goum]

Hi, I'm just wondering. If you mulitiply 1kg with 0.5kg you get 0.5kg

But if you do the multiplication in grams you get
1000g *500g = 500.000g = 500kg. a dompletely different result.

Why is that? How do you avoid this problem?

No, when you multiply 1kg with 0.5 kg you get 0.5 kg² - square kilograms. You must also multiply the units!

1000g *500g = 500 000 g²

Now, to convert square kilograms to square grams,

1kg * 1kg = 1000 g * 1000 g = 1 000 000 g²

So, now we take 500 000/ 1 000 000 g² = 0.5 kg². Precisely the same result.

 

[ShayanJ]

$1 \ kg \ \times \ 0.5 \ kg=0.5 \ (kg)^2=0.5 \ \times \ 10^6 \ g^2$
$1000 \ g \ \times \ 500 \ g=0.5 \ \times \ 10^6 \ g^2$

 

[Mark44]

Hi, I'm just wondering. If you mulitiply 1kg with 0.5kg you get 0.5kg

Without any context, I can't think of any reason you would want to multiply two quantities in kilogram units.

As already posted, the units of the product would be kg², which by itself isn't very meaningful.

But if you do the multiplication in grams you get
1000g *500g = 500.000g = 500kg. a dompletely different result.

Why is that? How do you avoid this problem?