Mental Arithmetic

What is in this deck

With this deck you learn mental arithmetic that holds up: times tables, squares, roots and percentages without paper.

7 × 8 is where most people stumble. The answer is written in its own digits: 5, 6, 7, 8.

This deck works through the whole times table to ten and then the one to twenty, plus the squares up to 25, the powers of ten and the roots worth knowing by heart. In the larger table every note shows the way: tens first, then the remainder.

Arithmetic is not authored; nothing here is taken from anywhere.

The categories decide what comes up: start with “Powers of ten” alone and add the rest when you are ready.

What you learn

• The complete times tables to ten
• The times tables up to twenty
• A worked route for every larger product
• Squares up to 25 and their roots
• The tricks for nines and numbers ending in 5

The categories

5 categories sort the 249 cards. You can filter by category and take on what is due right now.

1. Powers of ten
2. Square numbers
3. Square roots
4. Times tables to ten
5. Times tables to twenty

Learning with Qardbox

You see a card, you think, you turn it over and say whether you knew it. A round asks nothing more of you, and how the app works out the next date from that is on the page about FSRS-6.

What sits comes back less often, what wobbles comes back soon. You set a daily goal, and when nothing is due the app tells you exactly that instead of inventing work for you. How a round goes is shown on the learning page.

Everything stays on your device. No account, no sign-up, no ads. After the purchase the deck sits in your library like any other subject and can be studied, reordered and extended just like your own.

What it costs, and what it doesn’t

Qardbox itself costs nothing, and it stays that way. Every function is there from the start, with no subscription, no ads and no tiers; what that rests on is on the page about what it costs.

Your own cards stay unlimited, and decks from friends or from the family you read in without a limit, from a file as well. You do not need this deck in order to learn with Qardbox.

This deck costs nothing. Its 249 cards are checked and save you the work you would otherwise have.