What you’ll learn
Use units in multi-step problems.
Key idea
Multiply each rate by its own time to obtain compatible distance quantities before summing.
Rate times duration produces distance; sum only compatible quantities and track inverse-time units.
Worked example
Enter the exact value or ordered values in the format requested below.
A traveler goes 5 km/hour for 2 hours, then 10 km/hour for 3 hours. Compute total distance; enter numerical kilometers, omitting unit.
- Rate×time cancels hours: 5×2=10 km and 10×3=30 km.
- Total=10+30=40 km. Reversing second stage: (40-10)/10=3 hours.
Answer: 40
Quick Check
Evaluate a worked attempt at use units in multi-step problems, identify the first invalid step, and provide the correction.
A traveler goes 5 km/hour for 3 hours, then 18 km/hour for 4 hours. Step 1 gives 15 km for first stage. Step 2 gives 72 km for second stage. Step 3 calls 5+18=23 km the total distance. Locate the first invalid step and correct it.