Combining Digits – Easy as 1 2 3 4
Here are some ways to get 0 and 1 using 1, 2, 3, and 4.
0 = 1 + 4 – 2 – 3
0 = (3 – 1 – 2) * 4
1 = (2 – 1) * (4 – 3)
1 = 4 – 3 * (2 – 1)
THE CHALLENGE
How many numbers can you get using each of the numbers 1, 2, 3, and 4 in any order, using addition, subtraction, and multiplication?
EXPLORATION
How many more numbers can you make if you are also allowed to make two-digit numbers with the digits? For example, 26 = 24 + 3 – 1.
Notes
THE CHALLENGE:
Here are some solutions, with one missing, from 0 to 21. Of course, there are many more. Have fun comparing different people’s solutions!
0 = 1 + 4 – 2 – 3
1 = 4 – 3 * (2 – 1)
2 = (2 – 1) + (4 – 3)
3 = 4 – (3 – 2 * 1)
4 = 4 * (3 – 2*1)
5 = 4 + (3 – 2*1)
6 = 4 + 3 – 2 + 1
7 = 4 + 3 * (2 – 1)
8 = 4 * (3 – (2 – 1))
9 = 3 * (4 – (2 – 1))
10 = 1 + 2 + 3 + 4
11 = 3 * 4 – (2 – 1)
12 = 3 * 4 * (2 – 1)
13 = 3 * 4 + (2 – 1)
14 = 2 * (3 + 4) * 1
15 = 2 * (3 + 4) + 1
16 = 2 * (1 + 3 + 4)
17 =
18 = 4 * (3 + 1) + 2
19 = 4 * (2 + 3) – 1
20 = 4 * (2 + 3) * 1
21 = 4 * (2 + 3) + 1
EXPLORATION
Here are solutions up to 37 making use of two-digit numbers.
18 = 23 – 4 – 1
19 = 23 – 4 * 1
20 = 24 – 3 – 1
21 = 24 – 3 * 1
22 = 2 * 13 – 4
23 = 4 * 3 * 2 – 1
24 = 4 * 3 * 2 * 1
25 = 2 * 14 – 3
26 = 24 + 3 – 1.
27 = 23 + 1 * 4
28 = 23 + 4 + 1
29 = 32 – 4 + 1
30 = (4 + 1) * 3 * 2
31 = 34 – 2 – 1
32 = 34 – 2 * 1
33 = 34 – 2 + 1
34 = 34 * (2 – 1)
35 = 34 + 2 – 1
36 = 34 + 2 * 1
37 = 34 + 2 + 1