The carry, done the abacus way: when a digit will not fit on its rod, take ten from the rod to its left and give back the difference.
4 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
98
− 93
+ 48
− 44
?
2
36
+ 46
+ 89
− 69
?
3
85
− 68
+ 47
− 46
?
4
65
+ 62
+ 72
+ 49
?
5
43
− 39
+ 26
+ 46
?
6
78
+ 20
− 95
+ 53
?
7
65
+ 74
− 39
+ 75
?
8
93
+ 56
− 58
+ 28
?
9
44
− 13
+ 56
− 19
?
10
44
− 26
+ 38
− 51
?
Full answer key
98 − 93 + 48 − 44 = 9
36 + 46 + 89 − 69 = 102
85 − 68 + 47 − 46 = 18
65 + 62 + 72 + 49 = 248
43 − 39 + 26 + 46 = 76
78 + 20 − 95 + 53 = 56
65 + 74 − 39 + 75 = 175
93 + 56 − 58 + 28 = 119
44 − 13 + 56 − 19 = 68
44 − 26 + 38 − 51 = 5
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About this drill
Big friends are the pairs that add to ten: 1–9, 2–8, 3–7, 4–6, 5–5. To add 7 to a rod showing 6, you cannot — so you add one bead on the rod to the left (worth ten) and remove three on the right, because 7 is 10 minus 3. On paper this is called carrying. On the abacus it is a single two-handed gesture, and it is the last mechanical rule the method needs.
These drills stack four two-digit numbers with mixed signs, which is where big friends and small friends start appearing in the same problem. That combination is the real difficulty of this level — not either rule alone, but switching between them without pausing.
How to practise it
1Memorise the five pairs to ten before starting.
2Left hand on the tens rod, right hand on the units rod.
3Add the ten first, then remove the complement — always that order.
4Watch for problems needing both a small and a big friend in one row.
Where this sits
Level 4 — Elementary B
Big friends — the 10-complement rules — on 2-digit problems.
It produces the same result, but the procedure is different. Written carrying defers the ten to a later step; the abacus moves it immediately, so there is never anything held in reserve.
Why do both hands move?
Because two rods change at once. Training both hands from the start is what keeps speed up later — one-handed abacus work hits a ceiling fast.
My child mixes up small and big friends.
Normal at this stage. The cue is which bead is blocked: if the five-bead can solve it, it is a small friend; if the whole rod is full, it is a big friend.
How many digits should we practise on?
Two is right for learning the rule. Widen to three only after the two-rod carry is automatic, or the child ends up managing place value instead of the technique.