Question 11
In summer, New Zealand (GMT +12) uses daylight saving time, which is one hour ahead of New Zealand standard time. Western Australia (GMT +8) does not use daylight saving time.
When it is midday in summer in New Zealand, what is the time in Western Australia?
That’s it. Step through the hints below to see why. In 2025, 61.9% of Queensland students chose (A).
Not quite. 9 am comes from taking the daylight saving hour off New Zealand, which makes it GMT +11 and the gap 3 hours. Daylight saving puts clocks forward, so summer New Zealand is GMT +13 and the gap grows to 5 hours. In 2025, 20.9% of Queensland students chose (B).
Not quite. 3 pm is midday plus 3 hours, so two things went the wrong way. The daylight saving hour belongs on New Zealand’s side, making the gap 5 hours, and Western Australia sits west of New Zealand, so its clocks are behind. In 2025, 5.6% of Queensland students chose (C).
Close. 5 hours is the right gap, but you added it. Western Australia is further west than New Zealand, so the sun reaches it later and its clocks read earlier: midday minus 5 hours. In 2025, 10.8% of Queensland students chose (D).
This is the question. Summer New Zealand is GMT +13, so Western Australia is 5 hours behind and reads 7 am.
Standard time only. The gap shrinks to 4 hours and Western Australia reads 8 am. That isn’t an option, which is the QCAA telling you the daylight saving hour matters.
Move the New Zealand clock. Western Australia always reads hours earlier, because it sits further west.
Fix New Zealand’s summer offset first. Daylight saving puts the clocks one hour ahead of standard time.
$$\text{NZ summer}=\text{GMT}+12+1=\text{GMT}+13$$
Western Australia doesn’t change, so it stays on GMT +8.
Subtract the offsets to get the gap. The bigger offset is further east, and further east is ahead.
$$13-8=5\text{ hours}$$
New Zealand is ahead, so Western Australia is 5 hours behind.
Count back 5 hours from midday.
$$12\text{ noon}-5\text{ h}=7\text{ am}$$
Check the direction: the sun rises over New Zealand before it reaches Perth, so Perth’s clock should read earlier. Any pm answer has the direction backwards.
$$\begin{aligned}\text{NZ summer}&=\text{GMT}+13\\\text{time difference}&=13-8=5\text{ hours}\\\text{WA time}&=12\text{ noon}-5\text{ h}=7\text{ am}\end{aligned}$$
Add the daylight saving hour to New Zealand, find the gap, then count back because Western Australia is further west.
Only mark this done when you could do it without help. Reading the solution does not count.
Question wording is from the 2025 QCAA General Mathematics external assessment, © State of Queensland (QCAA) 2025, licensed under CC BY 4.0, and has been adapted. Tangent Tuition is not affiliated with the QCAA.
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