A higher resolution is required to access the IDE

- 32

## Learning Opportunities

This puzzle can be solved using the following concepts. Practice using these concepts and improve your skills.

## Statement

## Goal

You will be given 3 measurements (in centimeters) of a drinking-glass, sitting on a bar:===== Summary and your task =====

• its

`bottomRadius`

• its

`topRadius`= the radius of the lip (this is always larger than

`bottomRadius`)

• its height,

`glassHeight`

And you will be given a volume of beer

`beerVol`in cubic-centimeters (also known as milliliters) that's been poured into the drinking-glass.

How high up (

`beerHeight`) in the drinking-glass does the beer go ?

The above-described drinking-glass (upside down) in geometry is called a frustum.===== Geometry background: frustum =====

Wikipedia describes it thus:

"A cone with a region including its apex cut off by a plane is called a truncated cone; if the truncation plane is parallel to the cone's base, it is called a frustum."

The volume of conical frustum is:

V = (1/3) * π * h * (r² + r * R + R²)

...where r and R are the radiuses and h is the height.

But remember the radius of the top of the drinking-glass

**isn't**the radius of the top of the beer.

To better understand frustum geometry, you can experiment with:

https://www.omnicalculator.com/math/truncated-cone-volume

https://rechneronline.de/pi/truncated-cone.php

Tips:===== Oh, tricky =====

Your first instinct might be to try an Analytic solution, by simply plugging numbers into a formula.

But there are 4 elements, and you'd need to know 3 of them; but you only know 2 ☹️

These elements are:

• volume of the beer

`beerVol`

• bottom radius of the drinking-glass

`bottomRadius`

• height of the beer (unknown)

• radius of the drinking-glass at the spot where the top of the beer is (unknown)

So Analytic solution might be a bit tricky.

Perhaps try an Iterative method instead.

• Beer foam doesn't matter. Think of it as water instead if you prefer===== Notes, sources =====

• https://en.wikipedia.org/wiki/Cone#

• https://en.wikipedia.org/wiki/Iterative_method

Input

**Line 1:**4 floats separated by a space:

`bottomRadius`

`topRadius`

`glassHeight`

`beerVol`

Output

**Line 1:**A float,

`beerHeight`rounded and displayed to the nearest tenth

Height is measured perpendicular to the bar

Constraints

0 <

0 <

0 <

`beerHeight`<`glassHeight`< 500 <

`bottomRadius`<`topRadius`< 500 <

`beerVol`< 5000Example

Input

2.5 4 15 473

Output

14.3

A higher resolution is required to access the IDE