Quick answer
Convert the duration to a single unit, multiply by the factor, then convert the product back to hours, minutes and seconds.
Step by step
- Use minutes for whole-minute blocks or seconds if the input includes seconds.
- Multiply the total by the count or positive factor. Keep any fraction until the end.
- Convert back using groups of 60. If the output has to be whole seconds, round at the end and say which rounding rule you used.
Worked examples
Repeat a fixed block
45 minutes × 3 = 135 minutes, or 2 hours 15 minutes.
Scale by a fractional factor
1:20:00 is 4,800 seconds. Multiply by 1.25 to get 6,000 seconds, or 1:40:00.
Round for display
15 seconds × 1.5 = 22.5 seconds exactly. To the nearest second with half-up rounding, that is 23 seconds.
What to check
For three identical blocks, adding the same duration three times gives the same result. If the blocks have different lengths, add each one separately.
Related guides
Sources
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