SpeedJack 21 vs Probability(Math Drills)
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
SpeedJack 21
Practice your blackjack basic strategy with this educational app. Achieve consecutive correct answers to rank your time record on the server and improve your casino winning average.
- Blackjack basic strategy practice
- Consecutive correct answer challenge
- Server-based time ranking
- Improve casino winning average
- User sign-in required for challenges
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It is an application which helps your blackjack skill. You can practice basic strategy of blackjack with this application. If you succeed 20 times consecutive correct answer, your time record spent will be ranked on the server. Please sign-in before challenge. If you can pass this challenge easily without failing in short time, your winning average at the casino will be increasing.
Probability(Math Drills)
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You can learn Probability offline. Since the question generation and the correctness judgment of the answer are automatically performed, you can work on the drill learning as many times as you like. You can also see tips and answers. Score high in Challenge Mode to improve your rank!!
Screenshots
Verdict
The clearest difference is ads: Probability(Math Drills) at none against SpeedJack 21's shown. On price, update cadence, in-app purchases and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
SpeedJack 21 ships an update fortnightly, Probability(Math Drills) every 3 weeks. The most recent releases landed on September 16, 2026 and September 26, 2026 respectively.
| Parameter | SpeedJack 21 | Probability(Math Drills) |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) — better | — |
| Number of ratings | 1 — better | — |
| Update frequency | Fortnightly — better | Every 3 weeks |
| Ads | Yes | No — better |
| In-app purchases | No | No |
| Monetization | Ad-supported | — |
| Devices | iPhone, iPad, iPod — better | iPhone, iPod |
| Requires iOS | 13.0 | 12.0 — better |
| Further details — not scored | ||
| Size | 86 MB | 28 MB |
| Age rating | 12+ | 4+ |
| Developer | KwangRim Ahn | 郷 田村 |
In-app purchases
SpeedJack 21
No in-app purchases
Probability(Math Drills)
No in-app purchases
Questions
Is SpeedJack 21 free?
Is Probability(Math Drills) free?
Do SpeedJack 21 or Probability(Math Drills) have ads?
Which is updated more often, SpeedJack 21 or Probability(Math Drills)?
Other comparisons
