Ello, I'm a little stuck on these three questions.

The length of a rectangle is 8cm and its width is 3cm. What is the effect on the area of the rectangle when all of its dimensions are multiplied by 1/4?

The new area will be (1/4)^2   =  1/16  of the original area   .......[the square of the scale factor]

The surface area of a sphere is 100(pi symbol) cm^2. What is the volume of the sphere? Answer in terms of (pi symbol)

We need to find the radius......so we have

100pi =  4pi r^2   divide by pi

100 = 4 r^2          divide by 4

25  = r^2           take the square root of both sides

5 = r

So the volume =

(4/3) pi (5)^3  =  [ 125 * 4 ] / 3 * pi  =   [500/3] pi units^3

Triangle BCD is a right triangle. The length of the hypotenuse is 20cm. The length on one of the legs is 15cm. What is the length of the other leg? Round answer to the nearest tenth. 

The length of the other leg  = √[ 20^2 - 15^2]  = √[400 - 225]  = √175 ≈ 13.2 cm