Signs that change without warning, so there is no rhythm to settle into and no shortcut to fall back on.
6 rows × 2 digits, add & subtract
About 8 min
Free, no account
Sample problems
Real problems from this drill, with answers. Nothing to install, no account, no email — work them on paper, on a physical abacus, or in your head.
1
22
+ 38
+ 16
− 38
− 20
+ 61
?
2
38
+ 81
− 96
+ 74
− 78
+ 66
?
3
43
+ 19
− 38
+ 48
+ 17
+ 93
?
4
85
+ 93
+ 27
− 31
− 65
+ 55
?
5
68
− 41
− 20
+ 33
+ 58
+ 68
?
6
97
− 39
+ 85
− 95
+ 32
− 25
?
7
99
+ 24
− 16
+ 43
+ 91
− 57
?
8
90
+ 42
+ 72
− 52
+ 89
− 60
?
9
11
+ 26
+ 41
+ 27
− 44
+ 72
?
10
83
+ 11
− 38
− 14
+ 76
+ 53
?
Full answer key
22 + 38 + 16 − 38 − 20 + 61 = 79
38 + 81 − 96 + 74 − 78 + 66 = 85
43 + 19 − 38 + 48 + 17 + 93 = 182
85 + 93 + 27 − 31 − 65 + 55 = 164
68 − 41 − 20 + 33 + 58 + 68 = 166
97 − 39 + 85 − 95 + 32 − 25 = 55
99 + 24 − 16 + 43 + 91 − 57 = 184
90 + 42 + 72 − 52 + 89 − 60 = 181
11 + 26 + 41 + 27 − 44 + 72 = 133
83 + 11 − 38 − 14 + 76 + 53 = 171
Practise it now
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About this drill
Pure addition columns and pure subtraction columns both let a learner settle into a groove. Mixed columns remove that. Each row requires reading the sign, choosing the direction, and then choosing between a direct move and a complement — three decisions instead of one, repeated six times with no pattern to anticipate.
This is the drill shape used in most abacus examinations for exactly that reason, and it is the most honest measure of whether a technique is genuinely automatic or merely well-rehearsed in one direction.
How to practise it
1Read the sign before the number, every single row.
2Do not scan ahead for an easier ordering — work strictly top to bottom.
3Keep the same pace on plus rows and minus rows.
4If you hesitate twice on the same rule, drill that rule on its own page.
Questions
Why is mixed harder than either alone?
Because the decision cost is per row rather than per column. In a pure column you choose the direction once; in a mixed column you choose it six times.
Can the running total hit zero mid-problem?
It can reach zero but never pass below it. The generator guarantees this, matching what a physical soroban can display.
Is this what abacus exams use?
Broadly yes. Most graded abacus examinations use mixed columns because they cannot be passed by drilling one direction.
How do I get faster at these?
Not by hurrying. Isolate whichever rule causes the hesitation, drill it alone until it is silent, then come back to mixed.