Question

what is the difference between average and instantaneous speed

Answer 1

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Answer 2

Instantaneous--speed at an instant
average speed --total effect of speed...(Total distance/Total time)

Answer 3

average speed is the average of speed of an object over a span of time.
i.e. speed of an object need not stay constant over time so average speed is often used
while instantaneous speed is speed at a particular instant or time.