Q1
Speed and time for a fixed distance are:
Ainversely proportional
Bdirectly proportional
Cunrelated
Dalways equal
CBSEClass 8 (CBSE)MathematicsCh 10 · Topic 2
Solving Inverse Proportion Problems
Applying inverse proportion to solve time-work and speed-related problems.
Core concept
For example, if a car travels a fixed distance in 4 hours at 60 km/h, the total distance (speed × time) is 240 km — a constant regardless of how the speed changes. To find the time taken at 80 km/h for the same fixed distance: 240 = 80 × time, so time = 240/80 = 3 hours. This method is widely applicable to problems involving speed and time, workers and days, or any scenario where increasing one factor proportionally decreases another to complete the same fixed task or cover the same fixed distance.
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• Inverse proportion problems keep the product of two quantities constant across scenarios.
• Example: distance = speed × time (constant distance); if speed increases, time decreases proportionally.
• For 240km distance: at 60km/h takes 4hrs; at 80km/h takes 240/80=3hrs.
• This method applies to speed-time, workers-days, and similar fixed-task problems.