Finding elapsed time

Problem types

• Elapsed minutes
• Start, end and elapsed time in hours and minutes

Builds on

• Telling time to five minutes
• Converting to a smaller unit · Useful idea

  An elapsed time that crosses an hour is simpler when the hours are renamed as minutes: the same renaming of larger units as smaller ones lets the minutes be added and subtracted.

• Finding a missing number · Useful idea

  Start time plus elapsed time equals end time, so an unknown elapsed time or start time is an unknown addend.

Leads to

• Finding a unit rate · See it applied

  A rate such as miles per hour divides a quantity by elapsed time.

• Unit rates with fractions · See it applied

  A speed in miles per hour divides a distance by elapsed time, so elapsed time of a fraction of an hour gives a fractional unit rate.

• Average rate of change · Extend the idea

  Average rate of change divides the change in a quantity by the time elapsed, which generalises distance divided by elapsed time.

Related skills

None listed.