Problem 2 · Multiplication with equal groups · 3 points
Made by AI and not reviewed by a real person.
Mia’s toy building has 3 floors and 12 windows, with the same number on each floor. She adds 2 matching floors, then covers one window on each floor with a sticker; how many windows are left uncovered?
- 15
- 12
- 20
- 17
- 18
Show a hint
- Picture what happens to the windows on one floor when its sticker goes on. Remember that the new floors get stickers too.
- Find how many windows are on one floor, then how many remain uncovered on that floor. How many floors does the finished building have?
Show the answer and solution
Answer: A — 15
The original 3 floors have 12 windows, so each floor has 4. A sticker leaves 3 windows uncovered on each floor. There are now 5 floors, so 5 × 3 = 15 windows are uncovered. The tempting answer 17 counts stickers on only the 3 original floors, not the 2 new ones.