# yonjuu 四十

About

Yonjuu (meaning the number 40 in the Japanese language) is a fun math game developed by Hattennoki’s founder Jaspreet Sethi to build number sense, logical reasoning, and strategic thinking in children 3+ years and grown-ups.

Email us at jaspreet@hattennoki.com to purchase the game for your school/institution/home or book a demo session with your school, teachers, business, or apartment to learn how to adapt the game to different age groups and levels of math enthusiasts.

What's inside the box?

The deck consists of 44 cards consisting of four coloured 0-10 number cards.

Objective of the basic version of the game

Reach the target number of 40 (Yonjuu) using all the cards distributed.

Setup

Minimum players: 2

Maximum players: 6

If there are more than 2 players, seat them in a circle.

Gameplay (Basic Version)

1. A player shuffles the deck and distributes 6 cards to each player face down.

2. The remaining cards are kept in a draw pile.

3. Players then place their 6 cards face up on a flat surface for personal viewing.

4. Players check the sum of their 6 cards before beginning to play.

5. Players take turns to pick a card from the draw pile and check if the card helps them get closer to the target number (40).

6. If the card helps, the player keeps it and replaces one card from their set of 6 in a separate discard pile face down.

7. If a player cannot make a move that gets them closer to the target number, they must put the card back in the discard pile.

8. All players must continue playing in sequence and resetting their six cards as needed to reach a sum of the target number.

9. To win, a player must reach the target number first and shout "Yonjuu" while revealing all their 6 cards for show.

10. If all the cards from the deck finish, shuffle the discard pile to reuse the cards to pick from.

11. If a player shouts "Yonjuu" by mistake and hasn't reached the target number, they are considered out, but the rest of the players can continue playing.

12. If no one reaches the target number with one reshuffle of the discard pile and a replay, the player with the highest sum wins.

Variations

The game can have variations like selecting higher or lower target numbers.

Target numbers could be modified and/or specific colour combinations can be used, such as a sum of 45 with no blue, a sum of 30 with only red and blue, or a sum of 36 using only green and black.

Alternately, 4 cards instead of 6 can be used with mathematical operations beyond addition. For example, you can make 40 with 4 cards 2, 5, 7, and 10 as follows: (10 divided by 2) + (5 times 7)

Some possible ways to make 40 using 6 cards (there are more)

10 + 9 + 7 + 6 + 5 + 3 = 40

10 + 9 + 8 + 6 + 5 + 2 = 40

10 + 9 + 8 + 7 + 4 + 2 = 40

10 + 10 + 7 + 6 + 5 + 2 = 40

10 + 8 + 8 + 7 + 7 + 0 = 40

9 + 9 + 8 + 7 + 6 + 1 = 40

9 + 9 + 7 + 7 + 6 + 2 = 40

9 + 9 + 6 + 6 + 6 + 4 = 40

9 + 9 + 8 + 7 + 5 + 2 = 40

8 + 8 + 8 + 8 + 6 + 2 = 40

8 + 8 + 8 + 7 + 7 + 2 = 40

8 + 8 + 8 + 7 + 6 + 3 = 40

8 + 8 + 7 + 7 + 6 + 4 = 40

7 + 7 + 7 + 7 + 7 + 5 = 40

7 + 7 + 7 + 7 + 6 + 6 = 40

Advance Yonjuu Possibilities

For advanced players, upon prior mutual agreement, several other valid mathematical operations such as mod, square root, exponent, percentages, and the like can be used. Below are just a few examples:

(10 + 10) – (0 ÷ 6) + (4 * 5) = 40

(8 * 4) + (10% of 10) + (square root of 9) + 4 = 40

(10 mod 7) * (4^2) – (5+3) = 40

Yonjuu Adaptations for Early Years

The same cards can be used to develop number sense and build numeracy in young children. Below are just a few examples:

Recognize, organize, and classify the cards on the basis of colors/shapes/numbers/magnitude.

Find two cards with a sum of 5.

Find two cards with a difference of 2.

Identify cards that make partners of 6-10.

Use any 2 or more of the 6 cards distributed in creative ways to make a number higher than 10.

Use the cards to understand place value and build numbers under 50.

Ways to Introduce Yonjuu Cards to Beginners (Pre-Game Play Tasks)

1. Let them identify the cards and their shapes and colors.

2. Give them a card. Let them identify what number comes before and what comes after.

3.Give them two cards. Ask them which one is bigger and which one is smaller. The number of shapes in the frames will help them visually understand magnitude.

4. Give them two cards. Let them build the same two cards using unifix cubes, Legos, or blocks.

5. Start giving them two cards to compare differences or sums.

All of these are standalone tasks, and one task may be focused on at a time.

If the player has progressed beyond this stage, you can move on to the next level, which looks something like this:

1. Ask them to verbally identify the partners of 10 for any card distributed. (Partners of 10 are numbers that add up to 10, such as 6 and 4, 3 and 7, as well as 5 and 3, and 2, to name a few.)

2. Another task is to randomly give them 4 cards and have them identify any two cards that have a difference of 0 (i.e., the same number but different colors).

3. Next, give them 4 random cards and ask them to identify any two cards that have a difference of 1 (e.g., 5 and 6, 8 and 9).

4. Then, have them identify any two cards that have a difference of 2 (e.g., 5 and 7, 8 and 10), and so on.

5. Arrange the cards in ascending and/or descending order.

7. Find the difference between the highest and lowest cards that were distributed.

8. Gradually introduce the concept of finding the sum of the 6 cards distributed by first identifying partners of 10 within the cards.

Again, all of these are standalone tasks, and one task may be focused on at a time.