Units and estimation
Weeks 1-2You can carry units through a calculation and catch a wrong answer because the units do not match. You can also make a rough estimate first, so a bad answer stands out.
- Convert 60 miles per hour into feet per second.
- Estimate an answer to one digit before computing, then compare the two.
- Cancel units through a chain of conversion fractions.
Worked example
Convert 60 miles per hour into feet per second
- 60 x 5280 = 316,800 feet per hour
- Divide by 3600 seconds in an hour
Answer88 feet per second
Most common mistakeMultiplying by 3600 instead of dividing: reporting over a billion feet per second, faster than light, which the units check catches instantly.