# PP+ Archimedes Principle vs The Excretory System

The clearest difference is price: The Excretory System at Free against PP+ Archimedes Principle's $1.99. The Excretory System also leads on iOS requirement (12.0 vs 18.0). On in-app purchases there is nothing between them.

The Excretory System is free to download; PP+ Archimedes Principle costs $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.

## The numbers

| Metric | PP+ Archimedes Principle | The Excretory System |
| --- | --- | --- |
| Price | $1.99 | **Free** |
| In-app purchases | No | No |
| Ads | No | — |
| Update frequency | Every 29 months | — |
| Size | 111 MB | 34 MB |
| Requires iOS | 18.0 | **12.0** |
| Devices | **iPad** | — |
| Age rating | 4+ | 4+ |
| Developer | [Polyhedron Learning Media, Inc.](https://appshunter.io/developer/458882328) | [Science Education Institute](https://appshunter.io/developer/1439710468) |

## What reviewers say

### PP+ Archimedes Principle

[App page](https://appshunter.io/ios/app/pp-archimedes-principle/id622367686)

**Features:** macOS Compatibility

**In-app purchases:** none


### The Excretory System

[App page](https://appshunter.io/ios/app/the-excretory-system/id6526484663)

**In-app purchases:** none


## Frequently asked questions

### Is PP+ Archimedes Principle free?

PP+ Archimedes Principle costs $1.99, with no in-app purchases.

### Is The Excretory System free?

The Excretory System is free to download, with no in-app purchases.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*