..Arithmetics and Magic .
Escola Sadako
Barcelona
Age:
10-11 years old

Aims:

  • To discover the strategy hidden in a game of magic.
  • To create magic cards.
  • To play the game with other children

Materials:
Some paper, pencils and a ruler
Cards with the following numbers on them:
1
3
5
2
3
6
4
5
6
8
9
10
16
17
18
7
9
11
7
10
11
7
12
13
11
12
13
19
20
21
13
15
17
14
15
18
14
15
20
14
15
24
22
23
24
19
21
23
19
22
23
21
22
23
25
26
27
25
26
27
25
27
29
26
27
30
28
29
30
28
29
30
28
29
30


Introduction:
The teacher plays the magic game with the pupils. A student thinks of a number between 1 and 30. The teacher shows the cards to the students and he/she says whether the number he/she has thought of is on the card or not. The teacher guesses the number. The game is repeated several times to give the pupils the opportunity to find out the strategy for guessing the number.

Main part:
After playing for a while, when the pupils guess the strategy, it is their turn to create their own cards and to write the numbers on them.
The pupils prepare the grids to complete the cards. The teacher and the pupils start working together on the blackboard:

  • They start with number 1, it begins a card.
  • Number 2 begins another card.
  • Number 3 is written on the first and on the second card because it is formed by 1+2.
  • Number 4 can't be formed by 1 and 2 so it is written on a new card.
  • Number 5 is formed by 1+4, so it is written on the first and on the third card.
  • Number 6 will be on the second and on the third card (the cards that begin with number 2 and number 4)...

After that the teacher lets the pupils continue the game on their own. Once they have finished they check their cards by writing the remaining numbers on the blackboard.

Round up:
 The pupils can decorate their cards and show this game to younger children.
Observations:
The pupils enjoy playing this game a lot while they are adding and splitting numbers at the same time. When the teacher explained the game, the children wanted to know the solution right away but by making them wait and experience the sense of magic they enjoyed themselves even more.