Units, Rates & Scientific Notation
Carry units through the problem, and let them cancel.
The rules
- Rate = amount / time. Convert units by multiplying by a fraction equal to 1.
- Scientific notation: a × 10ⁿ with 1 ≤ a < 10.
- To multiply, multiply the coefficients and add the exponents.
- Check that your final units match what is asked.
Watch out: Forgetting to convert minutes and hours before using a rate.
Worked example
A car travels 150 miles in 2.5 hours. What is its speed in miles per hour?
- Speed = distance / time.
- 150 / 2.5 = 60.
Answer: 60
Try it yourself
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