Lost in Time

Algebra Level 2

You're traveling from Bangkok, Thailand, to Los Angeles. The Thai time zone is about 14 hours ahead to the Western coast one, and the whole trip lasts about 20 hours.

When landing, however, you just realize that your watch has stopped exactly at the departure time, which reads 9 A.M. on October 27, 2015.

How many hours and days does the time in L.A. differ, compared to your dead watch?

-6 hours, same date -10 hours, -1 date -6 hours, +1 date +10 hours, same date +6 hours, same date +6 hours, +1 date

2 solutions

Kay Xspre
Oct 27, 2015

Set yourself at departure time, 9AM on October 27 in Bangkok. If the whole trip takes 20 hours, you will reach Los Angeles on 5AM on October 28 (in Bangkok time). Adjusting for timezone in Los Angeles by turning the Bangkok clock back 14 hours, Los Angeles time will be 3PM on October 27, thus, the time differences between Los Angeles and the dead clock is 6 hours in the same date.

This question is poorly written. If your watch is already set to 10/27 9am Bangkok time and you add a 20-hour flight, it would be 10/28 5am in Bangkok. But if the problem is saying that the Thai time zone is 14 hours earlier than Los Angeles, you wouldn't subtract 14 hours from 5am (already Bangkok time), you would add it, making the current time in Los Angeles 7pm, 10/28 (+10 hours, +1 day). The "correct" answer can only be so if the question is rewritten to state that the Thai time zone is 14 hours later than Los Angeles.

Ronald Sweeney - 5 years, 7 months ago

The Pacific Time Zone (observing daylight saving time) is UTC-07:00, while Thailand is UTC+07:00 year round, thus the east coast will have greater time at the specific time.

Let's say that the UTC time is 00:00, Bangkok will be 07:00 while Los Angeles will be 17:00 of the previous day.

Kay Xspre - 5 years, 7 months ago

This question was quite simple. Just imagine yourself in the same scenario and the solution comes naturally from within.

Debmeet Banerjee - 5 years, 7 months ago

Sorry for the flaw. We set the first countries to see the sun as Japan or Eastern Australia. So compared to the U.S., Asian countries will see the sun first, making the Asian time zones earlier than the Western ones. So to avoid confusion, I'll adjust the word to be "ahead" instead.

Worranat Pakornrat - 5 years, 7 months ago

Excellent, thank you. I wasn't contesting the correctness of the solution, just pointing out that point of confusion, based on semantics. Thanks again.

Ronald Sweeney - 5 years, 7 months ago

Henny Lim
Oct 27, 2015

I analyzed this problem in reverse, when compared with Kay's way.

I found departure time on LA was 1pm on Oct 26, which occurs at the same time with 3am on Oct 27 in Bangkok. Therefore I got "+6 hours, same date" when I compared LA time with Bangkok time.

One more thing that I did the comparison in order. LA was written first, so I picked plus sign rather than minus sign.

Lost in Time

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