Problem 10 · 2020 Math Kangaroo
Medium
Ratios, Rates & Proportions
distance-speed-timeproportion
Two little mice, one white and one dark, leave at the same time toward the cheese along the different paths shown (the little squares are all equal). They reach the cheese at the same moment. If the dark mouse runs 4.5 metres per second, how many metres per second does the white mouse run?
Show answer
Answer: B — 1.5
Show hints
Hint 1 of 2
Same start, same finish, same time - so speeds are in the same ratio as the path lengths.
Still stuck? Show hint 2 →
Hint 2 of 2
Count the unit edges each mouse travels; the white mouse's speed scales 4.5 by (white length / dark length).
Show solution
Approach: speeds are proportional to path lengths over equal time
- Both mice take the same time, so speed is proportional to distance.
- Counting the grid edges, the white mouse's path is one third the length of the dark mouse's path.
- Hence its speed is one third of 4.5 m/s, namely 4.5 x (1/3) = 1.5 m/s.
Mark:
· log in to save