+
0
1
2
3
4
5
6
7
8
9
10
0
0
1
2
3
4
5
6
7
8
9
10
1
1
2
3
4
5
6
7
8
9
10
11
2
2
3
4
5
6
7
8
9
10
11
12
3
3
4
5
6
7
8
9
10
11
12
13
4
4
5
6
7
8
9
10
11
12
13
14
5
5
6
7
8
9
10
11
12
13
14
15
6
6
7
8
9
10
11
12
13
14
15
16
7
7
8
9
10
11
12
13
14
15
16
17
8
8
9
10
11
12
13
14
15
16
17
18
9
9
10
11
12
13
14
15
16
17
18
19
10
10
11
12
13
14
15
16
17
18
19
20

Why does 1 + 10 = 11?

Let's start at 1.

Next, let's count 10 times.

Ready? ... 1, 21, 32, 43, 54, 65, 76, 87, 98, 109, 1110.

That's why 1 + 10 = 11.

Mathgrow

0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9