측정과 시간

A total length or distance is the sum of its segments, but only after every measurement is expressed in the same unit. Learners unify handspans and rulers, convert km/m/cm, and accumulate multi-leg distances. Matching units before combining is the habit that prevents the most common measurement errors.

Time arithmetic regroups at sixty (seconds, minutes) and at twelve/twenty-four (hours, AM/PM), with days and weekdays cycling on top. Problems find elapsed time between clock readings, future dates, and the error of a fast or slow clock. It is place-value regrouping in a mixed-base system.