Time, Currency & Conversions

Revise Time, Currency & Conversions for Mathematics 0580 (O Level) — revision notes and instant AI marking.

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1. Time Conversions — Essentials to Know

Time conversions are different from most maths because they don't use base-10 (decimal). Instead, we use different bases for each unit. You absolutely must memorize these conversions.

Conversion	Formula
Seconds to Minutes (÷60)	60 seconds = 1 minute
Minutes to Hours (÷60)	60 minutes = 1 hour
Hours to Days (÷24)	24 hours = 1 day
Days to Weeks (÷7)	7 days = 1 week
Weeks to Years (÷52)	52 weeks ≈ 1 year (plus 1 day)
Days to Years (÷365)	365 days = 1 year (366 in leap year)
Months to Years (÷12)	12 months = 1 year

Remember the Rhyme for Calendar Months: "Thirty days have September, April, June and November. All the rest have thirty-one, except February alone, which has twenty-eight days clear, and twenty-nine in each leap year."

Days in Each Month: Jan (31), Feb (28/29), Mar (31), Apr (30), May (31), Jun (30), Jul (31), Aug (31), Sep (30), Oct (31), Nov (30), Dec (31)

Q: Convert 315 minutes into hours and minutes.

2. 12-Hour Clock vs 24-Hour Clock

These are two different ways to display time. It's crucial to understand both and be able to convert between them.

12-Hour Clock (AM/PM)

Goes around twice per day. AM = midnight (12:00am) to midday (12:00pm). PM = midday (12:00pm) to midnight (12:00am).

24-Hour Clock

Runs continuously from 00:00 (midnight) to 23:59 (11:59pm). Written as four digits with a colon: HH:MM.

12-Hour Clock	24-Hour Clock	Explanation
12:00 am (Midnight)	00:00	Start of the day
9:37 am	09:37	Morning times: add leading zero
12:00 pm (Midday)	12:00	Noon
5:32 pm	17:32	Afternoon: add 12 to hour
11:45 pm	23:45	Late evening: add 12

Converting PM to 24-hour:

Quick Review Questions

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Also in the full note

3. Reading Analogue and Digital Clocks
4. Calculating Time Intervals (How Long Between Times?)
5. Using Bus and Train Timetables
6. Converting Between Time Zones
7. Money Calculations & Rounding
8. Exchange Rates & Currency Conversion
9. Converting Between Three Currencies
Concepts Checklist

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Time, Currency & Conversions