Problem 5 · Check every possible case · 4 points
Made by AI and not reviewed by a real person.
Nina has cards labeled 1, 2, 3, 4, and 5. She uses two different cards to make a two-digit number; how many numbers greater than 30 can she make if the two digits add to 6?
- 4
- 2
- 1
- 5
- 3
Show a hint
- Find the pairs of digits that add to 6. Think about what happens when you swap their places.
- Check each number against both rules: it must be greater than 30, and Nina cannot use a card twice.
Show the answer and solution
Answer: B — 2
The two-digit numbers using digits from 1 to 5 that add to 6 are 15, 24, 33, 42, and 51. The first two are too small, and 33 needs the 3 card twice. Only 42 and 51 work, so the answer is 2. The tempting answer 3 wrongly includes 33.