We have a brick of regular size. It weighs 4kg. How much do you think a similar brick, four times smaller, but made of the same material weigh?
The smaller brick is not only four times shorter than the first one, but it is also four times narrower and four times lower and therefore the ratio of the volume and weight is 4 x 4 x 4 = 64 times.
So 4kg/64 = 62.5 grams.