IMO Practice Test — Subtraction Strategies
6 Questions • 12 min • Olympiad level
12:00
Question 1 of 6
medium
Count up from 54 to 80. How much added?
16
26
36
46
Explanation: 54+6=60 then +20=80. Total:26
Question 2 of 6
medium
Easiest strategy for 90-40?
Subtract tens
Count up
Compensation
Make 10
Explanation: Subtract 4 from tens digit = 50
Question 3 of 6
hard
71-29 using compensation (subtract 30 then add back)?
40
41
42
43
Explanation: 71-30=41 then +1=42
Question 4 of 6
easy
If 9+6=15 then 15-9=?
5
6
7
8
Explanation: 15-9=6
Question 5 of 6
hard
Decomposition: 63-24 (break 24 into 20+4)?
35
39
41
43
Explanation: 63-20=43 then 43-4=39
Question 6 of 6
hard
47-10=37 then 37-5=32 to find 47-15. Which strategy?
Compensation
Counting up
Decompose subtrahend
Doubles
Explanation: Breaking 15 into 10+5 is decomposing