Lesson

Once we can tell the time on clocks, we can calculate times in the future or in the past. For example, if it was $3$3 p.m., half an hour later would be $3:30$3:30 p.m.

What time is shown on this clock?

**Think:** The hour hand is pointing between the $9$9 and the $10$10, which means it's in the $9$9th hour. The minute hand is pointing at the $7$7, which, using the counting method, is $35$35 minutes.

**Do: **The time is $9:35$9:35.

If the time now is the time displayed on the clock below:

**a)** What time is $2$2$\frac{1}{4}$14 hours from now?

**Think:** The current time is $3:30$3:30. Let's break up the time and add the hours then the minutes.

In $2$2 hours, it will be $5:30$5:30.

Another $15$15 minutes ($\frac{1}{4}$14 of an hour) will be $5:45$5:45.

**Do:** $5:45$5:45

**b)** What time is $5$5 hours and $20$20 minutes from now?

**Think:** We need to add $5$5 hours, then $20$20 minutes on to $3:30$3:30.

$5$5 hours after $3:30$3:30 is $8:30$8:30.

$20$20 minutes after $8:30$8:30 is $8:50$8:50.

**Do:** $8:50$8:50

**c)** What time is $3$3 hours and $42$42 minutes from now?

**Think:** This time I am going to add the minutes then the hours.

$42$42 ($30+12$30+12) minutes after $3:30$3:30 is $4:12$4:12.

$3$3 hours after $4:12$4:12 is $7:12$7:12.

**Do:** $7:12$7:12

Use linear scales and whole numbers of metric units for length, area, volume and capacity, weight (mass), angle, temperature, and time