Dimensional analysis physics help?

Question

okay Im really confused and only got 2 days to do 2 worksheets containing dimensional analysis.

We are using SI units in some cases and it confuses me more

heres the first question on the easier worksheet

Use Dimensional Analysis to determine each of the follwing questions:

1. Estimate the number of breaths taken by a person during 70 years.

I tried setting the question up but it just doesn't seem like a right answer. I tried online sites, but it confuses me more.

Help? and give me a good example. My week points are converting units, its been my weak point since starting it back in elementry or middle school.

Answer 1

Estimate how many breaths you take in a minute.  Look at a watch and count.  I count mine at about 15 if I'm just sitting at the computer.  15 breaths per minute will be what we start with.  Multiply by 60 because there are 60 minutes in an hour.  That gives us 900 breaths an hour.  Multiply by 24 due to24 hours in a day.  That gives us 21600 breaths in a day.  Multiply by 365, due to 365 days in a year, giving us 7.88 million breaths a year.  Multiply by 70 and we get about 552 million breaths in 70 years.