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Pulmonary Ventilation watch

1. Hey guys,
Can anyone explain to me this question. I'm really stuck with it, I already got the answer of it but can't understand why they have divide it by 3 instead of multiplying with 3?
Calculate the rate at which person A breathed air out of his lungs between 0 and 3 seconds. Show your working. Show your working. (0 = 6.5, 3 = 2.3)
The table is attached on the picture

Found this answer on the mark scheme 6.5 -2.3 = 4.2
4.2/3 = 1.4
2. (Original post by Hiyam torkamane)
Hey guys,
Can anyone explain to me this question. I'm really stuck with it, I already got the answer of it but can't understand why they have divide it by 3 instead of multiplying with 3?
Calculate the rate at which person A breathed air out of his lungs between 0 and 3 seconds. Show your working. Show your working. (0 = 6.5, 3 = 2.3)
The table is attached on the picture

Found this answer on the mark scheme 6.5 -2.3 = 4.2
4.2/3 = 1.4
You divide it by three because you're finding a rate. An answer of 1.4 cm³/s means that in every second from the start of measurement, the person breathed out 1.4 cm³ of air.
If you think about a car, for example, if you wanted to find its speed (or put another way, the RATE of change of displacement) you would divide the distance it travelled by the time it took to do so. It's a similar idea in your question. Rates are always found by dividing one variable by time.

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