Time Currency And Conversions

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Notes

Time Conversions

Time uses non-decimal units: 60 seconds $= 1$ minute, 60 minutes $= 1$ hour, 24 hours $= 1$ day.
Know days in each month: $e.g., \frac{28}{29}$ Feb, 30 Apr/Jun/Sep/Nov, 31 Jan/Mar/May/Jul/Aug/Oct/Dec.
To convert hours to minutes, multiply by 60; minutes to hours, divide by 60.
When calculating time intervals, work in chunks: minutes to next hour, then whole hours, then remaining minutes.
For journeys crossing midnight, add hours from start to midnight plus hours from midnight to end.

12-Hour and 24-Hour Clocks

12-hour clock uses AM (midnight to midday) and PM (midday to midnight).
24-hour clock uses four digits: first two for hours (00-23), last two for minutes (00-59).
Convert 12-hour to 24-hour: for PM (except 12pm) add 12; for $AM 12am = 00:00$ .
Convert 24-hour to 12-hour: subtract 12 from hours 13-23 and add PM; $00:00 = 12am, 12:00 = 12pm$ .
Analogue clock: short hand = hours, long hand = minutes (each number $= 5 minutes)$ .

Calculating with Time

Add time in chunks: add hours first, then minutes, adjusting if minutes exceed 60.
Subtract time by counting minutes to next hour, then hours, then remaining minutes.
For journeys starting and ending on same day, simply subtract start from end times.
For overnight journeys, calculate time from start to midnight plus time from midnight to end.
Use a calculator's ° ' '' button to enter time; 1 hour 30 $min = 1.5$ decimal hours.

Bus and Train Timetables

Timetables usually use 24-hour clock without colon (e.g., 0750 for 07:50).
Each column represents one service; times are departure times except last row (arrival).
Journey time = difference between departure at start and departure/arrival at end for same service.
Read across the row for a given service to find times at different stops.

Time Zones

Time zones differ by hours; some locations are ahead, others behind a reference (e.g., GMT).
To convert to a time zone behind, subtract the time difference; to one ahead, add.
When calculating flight times, work in departure local time then adjust to arrival local time.
Example: Madrid is 7 hours ahead of Chicago; a 9h45m flight from Madrid at 7:30am arrives Chicago at 10:15am local.

Money Calculations

Common currencies: US Dollar ($), Pound (£), Euro (€).
Keywords: 'total' means add, 'difference' means subtract, 'change' may involve exchange rates.
Round final answers to 2 decimal places for dollars, pounds, euros (e.g., $1.40 not $1.4).
For large amounts, round to nearest pound, ten pounds, or hundred as appropriate.
Use all decimal places given in working; round only final answer.

Exchange Rates

Exchange rate shows value of one currency in another (e.g., £1 = €1.17).
To convert from base currency to other, multiply by the exchange rate.
To convert from other currency to base, divide by the exchange rate.
If unsure whether to multiply or divide, check if result should be larger or smaller than original.
When converting via a third currency, convert to intermediate then to target.

Comparing Costs Across Currencies

Convert all prices to same currency using given exchange rates.
Compare converted values to determine which is cheaper or better value.
For best value, calculate cost per unit (e.g., per litre, per kg) in a common currency.
Round final comparison appropriately (e.g., nearest cent, nearest rupee).

Time Conversion Flowchart

24-Hour Clock Conversion

Currency Conversion Diagram

Time Zone Calculation Example

Practice questions

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1.Aimee changes 250 euros into dollars. The exchange rate is 1 euro = $1.10. How many dollars does she receive?
Easy
- A$275
- B$227.27
- C$260
- D$250
2.A train journey takes 5 hours 54 minutes. The journey starts at 09 15. What time does the journey end?
Easy
- A15 09
- B14 09
- C15 19
- D14 19
3.A train leaves Zurich at 22 40 and arrives in Vienna at 07 32 the next day. How long does the journey take?
Easy
- A8 h 52 min
- B9 h 08 min
- C8 h 48 min
- D9 h 52 min
4.Jodi swims 22 lengths of a swimming pool to raise money for charity. She receives $15 for each length she swims. How much money does Jodi raise?
Easy
- A$330
- B$37
- C$3300
- D$220
5.Carlos starts work at 21 20 and finishes at 06 15 the next day. How long is Carlos at work?
Medium
- A8 h 55 min
- B9 h 05 min
- C8 h 45 min
- D9 h 55 min
6.Linda wants to change up to £200 into koruna. The exchange rate is £1 $= 25.82$ koruna. She can only get 100 koruna notes and wants as many as possible. How many 100 koruna notes should she get?
Medium
- A51
- B52
- C50
- D53
7.One morning, Marcia works from 08 20 to 11 15. How long does she work for? Give your answer in hours and minutes.
Medium
- A2 h 55 min
- B3 h 05 min
- C2 h 45 min
- D3 h 15 min
8.Convert $0.17 m^{2}$ into $cm^{2}$ .
Hard
- A $1700 cm^{2}$
- B $17 cm^{2}$
- C $170 cm^{2}$
- D $0.0017 cm^{2}$

Summary

## Time, Currency & Conversions ### Time - **Conversions**: 60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day, 365 days = 1 year (366 in leap year). - **12-hour clock**: AM (midnight to midday), PM (midday to midnight). - **24-hour clock**: 00:00 (midnight) to 23:59. No AM/PM. - **Calculating time intervals**: Work in chunks – minutes to next hour, then whole hours, then remaining minutes. - **Time zones**: If ahead, subtract; if behind, add. Convert local times carefully. ### Money Calculations - **Keywords**: total (add), difference (subtract), exchange (multiply/divide). - **Rounding**: Usually 2 decimal places for dollars, pounds, euros. Write both decimals (e.g., $1.40). - **Large numbers**: Round to nearest whole number or as per question. ### Exchange Rates - **Convert from currency A to B**: Multiply by exchange rate (A → B). - **Convert from currency B to A**: Divide by exchange rate (B → A). - **Check**: If result is larger than original, you multiplied; if smaller, divided. Use logic. ### Key Tips - Use calculator's ° ' '' button for time. - 1 hour 30 min = 1.5 hours on calculator. - Always write currency symbol and correct decimal places.

Key terms

Exchange rate: The value of one currency in terms of another, used to convert between currencies.
24-hour clock: Time display using four digits (00:00 to 23:59) without AM/PM.
12-hour clock: Time display using AM (midnight to midday) and PM (midday to midnight).
Time zone: A region where the same standard time is used; differences are in hours ahead or behind GMT/UTC.
Currency: A system of money used in a country, e.g., USD, GBP, EUR.

Slides

Time Conversions

Time uses non-decimal units: 60 seconds $= 1$ minute, 60 minutes $= 1$ hour, 24 hours $= 1$ day.
Know the number of days in each month (e.g., 30 days in April, 31 in January).
Use chunking: add minutes to next hour, then whole hours, then remaining minutes.

How many minutes are there in 2 hours 15 minutes?

135 minutes
125 minutes
215 minutes
90 minutes

12-hour and 24-hour Clocks

12-hour clock uses AM (midnight to midday) and PM (midday to midnight).
24-hour clock uses four digits: 00:00 (midnight) to 23:59.
Convert: $12:00 AM = 00:00, 12:00 PM = 12:00, 5:32 PM = 17:32$ .

Convert 3:45 PM to 24-hour time: ____.

Calculating Time Intervals

To find duration, work in chunks: minutes to next hour, then whole hours, then remaining minutes.
For journeys crossing AM/PM or midnight, add hours carefully.
Example: 11:23 AM to 2:27 PM is 37 $min + 2 h + 27$ $min = 3 h 4$ min.

A train starts at 09:15 and takes 5 hours 54 minutes. What is the arrival time?

15:09
14:09
15:19
14:19

Time Zones

Different countries have different time zones (e.g., New York is 5 hours behind London).
To convert, add or subtract the time difference depending on which is ahead.
When flying, work in departure time zone first, then convert to arrival time zone.

Which of these are true about time zones?

If London is 5 hours ahead of New York, when it's 10:00 in London it's 05:00 in New York.
Time zones only affect hours, not minutes.
When converting flight times, you should always work in arrival time zone first.

Money Calculations

Read questions for keywords: total (add), difference (subtract), exchange (multiply/divide).
Round final answers to two decimal places for dollars, pounds, euros.
For large numbers, round to nearest whole number or as specified.

A shop sells fabric for $2.97 per metre. A customer buys 9 metres and pays with $50. How much change does he receive?

$23.27
$26.73
$22.73
$27.27

Exchange Rates

Exchange rate tells how much one currency is worth in another.
To convert from currency A to B, multiply if A is the base $(1 A = x B)$ .
To convert from B to A, divide by the rate.

Convert 250 euros to dollars if 1 euro = $1.10. She receives $____.

Exchange Rate Problems

Sometimes you need to convert via a third currency (e.g., USD to JPY to AUD).
Check if you expect a larger or smaller number to decide multiply/divide.
Always round appropriately at the end.

£1 $= 25.82$ koruna. Linda wants to change up to £200 into 100 koruna notes. How many 100 koruna notes should she get?

Comparing Costs Across Currencies

Convert all prices to the same currency to compare.
Use exchange rates to find equivalent values.
Example: Compare cost of petrol in UK (£1.24/L) vs USA ($3.15/gallon) using 1 gallon $= 3.79 L$ and £1 = $1.47.

Which statements are correct when comparing costs?

Always convert to the same currency before comparing.
You can compare prices directly if they are in different currencies.
Exchange rates may need to be applied to both price and units (e.g., per litre vs per gallon).

Summary

Time: convert units, use chunking for intervals, handle time zones.
Money: add/subtract costs, round to 2 decimal places.
Exchange rates: multiply or divide correctly, compare after conversion.

A train leaves Zurich at 22:40 and arrives in Vienna at 07:32 the next day. How long is the journey?

8 h 52 min
9 h 52 min
8 h 48 min
9 h 48 min

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