IMO Practice Test — Addition with Regrouping
6 Questions • 12 min • Olympiad level
12:00
Question 1 of 6
hard
Find the missing ones digit: 4_ + 18 = 65
5
6
7
8
Explanation: 65 − 18 = 47, so the missing digit is 7.
Question 2 of 6
hard
What is the sum of the smallest 3-digit number and the largest 2-digit number?
199
198
189
200
Explanation: 100 + 99 = 199.
Question 3 of 6
medium
250 + 250 + 250 = ?
650
700
750
850
Explanation: Three 250s = 750.
Question 4 of 6
hard
A number plus 167 gives 400. The number is…
233
243
223
333
Explanation: 400 − 167 = 233.
Question 5 of 6
medium
Add: 99 + 99 = ?
188
198
199
200
Explanation: 99 + 99 = 198 (think 100+100−2).
Question 6 of 6
hard
Which sum needs regrouping in BOTH the ones and tens?
23 + 14
45 + 32
58 + 67
21 + 11
Explanation: 58+67: 8+7=15 (carry), 5+6+1=12 (carry) — both columns regroup.