Lesson 7: Two-Digit Addition (27 + 15)
Intermediate Level
Instructions
- Let's add 27 + 15 across two columns.
- Set 27: In the tens column, slide 2 blue beads up (20); in the ones column, slide the red bead down (5) and 2 blue beads up (2).
- Add 15: In the tens column, add 1 blue bead (30 total); in the ones column, clear the 2 blue beads and red bead, then slide 2 blue beads up (7 + 5 = 12, carry 1 to tens).
- The value should be 42!
T
100B
10B
B
100M
10M
M
100K
10K
K
100
10
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
5
1
1
1
1
Value: 0