# Add and subtract within 20 vs Monsty

The clearest difference is update cadence: Monsty at every 6 weeks against Add and subtract within 20's every 36 months. Add and subtract within 20's advantage is iOS requirement (12.0 vs 15.1). On price, ads, in-app purchases and device support there is nothing between them.

Add and subtract within 20 costs $2.99 and Monsty $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Add and subtract within 20 ships an update every 36 months, Monsty every 6 weeks. The most recent releases landed on August 24, 2026 and August 21, 2026 respectively.

## The numbers

| Metric | Add and subtract within 20 | Monsty |
| --- | --- | --- |
| Price | $2.99 | $2.99 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 36 months | **Every 6 weeks** |
| Monetization | Paid | — |
| Size | 18 MB | 29 MB |
| Requires iOS | **12.0** | 15.1 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Sergey Malugin](https://appshunter.io/developer/562782409) | [PATRICIA SAUER](https://appshunter.io/developer/1697710298) |

## What reviewers say

### Add and subtract within 20

[App page](https://appshunter.io/ios/app/add-and-subtract-within-20/id757149544)

This app transforms math practice into an exciting adventure for children. It uses interactive mini-games and handwriting recognition to make learning addition and subtraction within 20 fun and effective. The difficulty adapts to your child's progress for a personalized experience.

**Highlights:** Interactive mini-games, Handwriting recognition, Adaptive difficulty, Targeted addition/subtraction practice, Natural learning input

**Features:** macOS Compatibility

**In-app purchases:** none


### Monsty

[App page](https://appshunter.io/ios/app/monsty-first-math/id6738328693)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Add and subtract within 20 free?

Add and subtract within 20 costs $2.99, with no in-app purchases.

### Is Monsty free?

Monsty costs $2.99, with no in-app purchases.

### Do Add and subtract within 20 or Monsty have ads?

Neither Add and subtract within 20 nor Monsty shows ads.

### Which is updated more often, Add and subtract within 20 or Monsty?

Add and subtract within 20 ships an update every 36 months, and Monsty every 6 weeks. Most recently, Add and subtract within 20 was updated on August 24, 2026 and Monsty on August 21, 2026.

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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.*