80% is the same as 4/5, so 4/5 of the class= 20. That means that if there was a picture, 4 parts would be shaded, and 1 would not. 1/4 of 20 is 5, so 1 part= 5 people. 5 x 5 = 25. 25 is the answer. :)

8 0

2 years ago

Read 2 more answers

Make r the subject of the formula <img src="https://tex.z-dn.net/?f=v%20%3D%20%5Cpi%20%5C%3A%20h%20%7B%7D%5E%7B2%7D%28r%20-%

Vaselesa [24]

Answer:

$\boxed{r = \frac{h}{3} + \frac{v}{\pi {h}^{2} } }$

Step-by-step explanation:

$Solve \: for \: r: \\ = > v= \pi {h}^{2}(r - \frac{h}{3} ) \\ \\ v=\pi {h}^{2}(r - \frac{h}{3} )is \: equivalent \: to \: {h}^{2}\pi(r - \frac{h}{3} ) = v: \\ = > {h}^{2}\pi(r - \frac{h}{3} ) = v \\ \\ Divide \: both \: sides \: by \: \pi {h}^{2} : \\ = > r - \frac{h}{3} = \frac{v}{\pi {h}^{2} } \\ \\ Add \: \frac{h}{3} \: to \: both \: sides: \\ = > r = \frac{h}{3} + \frac{v}{\pi {h}^{2} }$

8 0

2 years ago

What is the formula to calculate the surface area of a rectangular prism with a cube removed?

ch4aika [34]

2ab + 2bc + 2ac the formula for the rectangular prism and i'm guessing you would find the answer to this than you would find your formula for the cube which is 6 a 2 and you would find that answer.
You would take your total for the rectangular prism answer and subtract the cube answer from it and you would probably get your answer.
hope that helped?!
:)

3 0

2 years ago