Answer:
The mass of half a liter of water is 500g, that is, 0.5kg.
Step-by-step explanation:
Density is mass divided by the volume, that is:

Here, we have to be careful. Since the density is in grams per cm³, m has to be in grams and v in cm³.
We have that:

What is the mass of half a liter of water?
One liter is 1000 cm³.
So half a liter is 1000/2 = 500 cm³, which means that 
Then



The mass of half a liter of water is 500g, that is, 0.5kg.
When u divide 0.004 by 0.05 you will get 0.08 as the quotient.
<span />
it equals <span>(−<span>12</span>)</span> because <span><span>cos<span>(<span>60∘</span>)</span></span>=<span>12</span></span>
Explanation:
The reference angle for <span>240∘</span> is <span>60∘</span> (since <span><span>240∘</span>=<span>180∘</span>+<span>60∘</span></span>)
<span>60∘</span> is an angle of one of the standard triangles with
<span><span>cos<span>(<span>60∘</span>)</span></span>=<span>12</span></span>
<span>240∘</span> is in the 3rd quadrant so (either by CAST or noting that the "x-side" of the associate triangle is negative)
<span><span>cos<span>(<span>240∘</span>)</span></span>=−<span>cos<span>(<span>60∘</span>)</span></span></span>
<span><span>cos<span>(<span>240∘</span>)</span></span>=−<span><span>12</span></span></span>