Moving towards each other
Two people a distance apart walk or cycle towards each other, and a dog, a bird or a drone goes back and forth between them until they meet. The student works out how long it is until they meet, how far the dog runs altogether, or how far from one start they meet.
Following each of the dog's trips never ends. The trick is to find the time first: the gap shrinks by both speeds added together every hour, and once the time is known, the dog's distance is its speed times that time. The working marks where they meet on the road.
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What changes each time
- Walkers at 3 to 6 km/h, or cyclists at 8 to 16 km/h
- A dog, a bird or a drone, always faster than both
- Time to meet, distance run, or where they meet
More ratio, rates and percentages practice
- Equivalent fractions, percentages and ratios (Grade 4)
- Rate tables (Grade 4)
- Calculating speed (Grade 4)
- Calculating distance (Grade 4)
- Calculating travel time (Grade 4)
- Moving walkway speed (Grade 4)
- Average speed there and back (Grade 5)
- Percentage of a grid (Grade 5)
- Work and time problems (Grade 5)