A cubical block of metal weighs 6 kg. How much will another cube of the same metal weigh if its sides are twice as long?

48 kg

Step-by-step explanation:

Mass is proportional to volume, and volume is proportional to side³

W1/6 = 2³

W1 = 6 × 8

48

dy/dx = -1 /√(1 - x^2).

Step-by-step explanation:

y = arccos x.

So x  = cos y

dx / dy = - sin y

dy / dx = -1 / sin y

But sin y = √( 1 - cos^2 y)

But cos y = x , so cos^2y = x^2

Therefore  

dy/dx = -1 / √(1 - x^2).