Problem 14 · 2015 Math Kangaroo
Medium
Arithmetic & Operations
off-by-one
11 flags are placed alongside a straight race course. The first flag is at the start, the last one at the finish. The distance between two flags is always 8 meters. How long is the race course?
Show answer
Answer: D — 80 meters
Show hints
Hint 1 of 2
The flags are like fence posts: 11 flags do not make 11 gaps.
Still stuck? Show hint 2 →
Hint 2 of 2
Count the gaps between the flags, then multiply by 8 meters.
Show solution
Approach: count the gaps (one fewer than the flags)
- With 11 flags in a row there are 11 - 1 = 10 gaps between them.
- Each gap is 8 meters, so the course is 10 x 8 = 80 meters.
- That is choice D.
Mark:
· log in to save