🦘 Math Kangaroo Grade All Felix 1-2 Ecolier 3-4 Benjamin 5-6 Kadett 7-8 Junior 9-10 Student 11-12 ⇄ switch contest
2019 Math Kangaroo

Problem 15

Problem 15 · 2019 Math Kangaroo Medium
Spatial & Visual Reasoning reflectionspatial-reasoning

Four strips of paper are used to make a pattern (see picture). What do you see when you look at it from behind?

Figure for Math Kangaroo 2019 Problem 15
Show answer
Answer: D
Show hints
Hint 1 of 2
Looking from behind flips the picture left-to-right, like in a mirror.
Still stuck? Show hint 2 →
Hint 2 of 2
Also swap which strips are on top: whatever was over another strip is now underneath.
Show solution
Approach: mirror left-right and swap the over/under crossings
  1. Viewing from behind mirrors the whole pattern left to right.
  2. At every crossing, the strip that was on top is now hidden under the other.
  3. Applying both changes to the woven pattern gives option D.
  4. So the answer is D.
Mark: · log in to save
↑