Cynthia Lanius

Card No. 1
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31

Power Cards

A Mathematical Puzzle - Solution


Choose a number from 1-31. Tell me which cards the number is in, and I can tell you the number. How do I do it? Find out below.

 
Card No. 1
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
Card No. 2
2
3
6
7
10
11
14
15
18
19
22
23
26
27
30
31
Card No. 3
4
5
6
7
12
13
14
15
20
21
22
23
28
29
30
31
Card No. 4
8
9
10
11
12
13
14
15
24
25
26
27
28
29
30
31
Card No. 5
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

Let's say you pick 28. It is in cards 3, 4, and 5. Now look at those cards. Do you notice anything special? Add the first number of those three cards. Add 4 + 8 + 16. You get 28! What is so special about 4, 8, and 16?

Powers of 2! Notice that the first number of all the cards is a power of 2. We can add powers of 2 and make any whole number.

Print this page and dazzle your friends by playing the trick with them.

How to Create the Cards - Blank Cards


Power Cards Intro || Print Version || The Trick Explained || Blank Cards || Application - Binary Nos.
More of Cynthia Lanius' Math Lessons
URL http://math.rice.edu/~lanius/pro/power2.html