Subtracting positive and negative numbers

Difficulty Standard · Set eodyg5

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1
(-20)−26=
2
(-21)−6=
3
(-19)−(-30)=
4
3−(-8)=
5
17−(-6)=
6
(-29)−(-7)=
7
(-13)−13=
8
(-5)−10=
9
17−(-4)=
10
(-5)−(-27)=
11
(-29)−26=
12
15−(-6)=
13
(-11)−(-18)=
14
(-13)−23=
15
29−(-18)=
16
(-5)−(-23)=
17
(-24)−(-6)=
18
8−(-2)=
19
13−(-26)=
20
(-25)−28=

What is in this set

The numbers in this set run from 2 to 30.
71% of them have exactly one negative.
29% of them have a negative on both sides.
A careful solution takes 2 written steps on average.
The mistake this set invites most often, in 68% of the problems: taking away a negative was treated as taking away — subtracting a negative adds.
Answers are a whole number.

Drawing 240 problems from this page produced 231 different ones, 96% — so a sheet of 20 is a new sheet almost every time.

The same skill, harder or easier

We would put this in front of a grade 6 class. That is our judgement, not a standard, and it is printed here so you can disagree with it. Everything else we put in that year.