Year 8AC9M8M04

Time Zones and Duration

Solve problems involving duration, including using 12- and 24-hour time across multiple time zones.

Work in one time zone at a time. Convert first, then find the duration — never both at once.

Method

Convert, then calculate

Put both times into the same zone before subtracting.

East is ahead, west is behind

Moving east adds hours. Moving west takes them off.

Flight time is not the clock difference

A 2-hour flight can land at the same time it left.

Watch the date line

Adding hours can push you into the next day.

e.g.

\text{A flight leaves Perth at } 09{:}00 \text{ and lands in Sydney at } 15{:}30. \text{ Sydney is 3 hours ahead. Find the flight time.}

Choose one zone to work in. Use Perth time. $\text{work in Perth time}$
Convert the landing time back to Perth time. $15{:}30 - 3 = 12{:}30 \text{ Perth}$
Now both times are in the same zone. $09{:}00 \to 12{:}30$
Find the duration. Hours first. $09{:}00 \to 12{:}00 = 3 \text{ hours}$
Then the minutes. $12{:}00 \to 12{:}30 = 30 \text{ min}$
State the flight time. $3 \text{ hours } 30 \text{ minutes}$

Convert to one zone first. Then it is an ordinary duration question.

\text{It is } 14{:}00 \text{ in Perth. Sydney is 3 ahead. Sydney time?}

Answer

17{:}00

\text{It is } 08{:}00 \text{ in Sydney. Perth is 3 behind. Perth time?}

Answer

05{:}00

\text{A 4-hour flight leaves Sydney } 06{:}00, \text{ Perth is 3 behind. Landing time in Perth?}

Answer

07{:}00

\text{How long from } 22{:}40 \text{ to } 01{:}15 \text{ the next day?}

Answer

2 \text{ h } 35 \text{ min}

\text{Why convert before subtracting?}

Answer

\text{Subtracting across zones mixes two different clocks.}

\text{A flight lands before it left on the clock. Possible?}

Answer

\text{Yes, flying west across enough zones.}