Lesson objective: Understand why the :30 displayed on a digital clock represents the same thing as when the minute hand points to the six on an analog clock.

Students bring prior knowledge of reading analog and digital clocks from telling time to the hour and half hour. This prior knowledge is extended to push students to understand the meaning of a half hour as students think about how the two different formats of clocks are connected. A conceptual challenge students may encounter is misinterpreting the 30 on a digital clock as a six.

The concept is developed through work with digital and analog clocks, which shows students why it makes sense that a half hour is linked with the number 30.

This work helps students deepen their understanding of equivalence because it shows students that the 30 on a digital clock is the same as when the minute hand points to the six on an analog clock.

Students engage in Mathematical Practice 7 (look for and make use of structure) as they interpret the connections between representing half hours on digital and analog clocks.

**Key vocabulary:**

- Analog clock
- Colon
- Digital clock
- Half hour
- Half past
- Minute hand