# E4Keys vs Problems Involving Percent

The clearest difference is in-app purchases: Problems Involving Percent at none against E4Keys's 3. Problems Involving Percent also leads on iOS requirement (12.0 vs 15.6). On price, ads and device support there is nothing between them.

Both are free to download. E4Keys sells 3 in-app purchases, starting at $1.99 per month. Problems Involving Percent asks for nothing beyond the download.

## The numbers

| Metric | E4Keys | Problems Involving Percent |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Monthly | — |
| Size | 46 MB | 37 MB |
| Requires iOS | 15.6 | **12.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [CARLOS GOMES DE OLIVEIRA](https://appshunter.io/developer/1576926646) | [Science Education Institute](https://appshunter.io/developer/1439710468) |

## What reviewers say

### E4Keys

[App page](https://appshunter.io/ios/app/e4keys/id1604234563)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Assinatura Mensal | $1.99 | per month |
| Assinatura Semestral | $9.99 | per 6 months |
| Assinatura Anual | $14.99 | per year |


### Problems Involving Percent

[App page](https://appshunter.io/ios/app/problems-involving-percent/id6736588730)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is E4Keys free?

E4Keys is free to download, with in-app purchases available.

### Is Problems Involving Percent free?

Problems Involving Percent is free to download, with no in-app purchases.

### Do E4Keys or Problems Involving Percent have ads?

Neither E4Keys nor Problems Involving Percent shows ads.

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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.*