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Time - Conversion of Time Units

Grade 4ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Units of Time: Time is measured in various units including seconds, minutes, hours, days, weeks, months, and years. Imagine a circular clock face where the perimeter is divided into 6060 equal parts; each small part represents one minute for the minute hand and one second for the second hand.

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Conversion Rule (Bigger to Smaller): To convert a larger unit of time to a smaller unit, we always multiply. For example, to go from hours to minutes, we multiply by 6060. Visualize a downward arrow showing that as units get smaller, the numerical value increases through multiplication.

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Conversion Rule (Smaller to Bigger): To convert a smaller unit of time to a larger unit, we always divide. For example, to change minutes into hours, we divide by 6060. Visualize an upward arrow showing that as units get larger, the numerical value decreases through division.

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The 12-hour Clock: This system divides the 2424 hours of a day into two periods. The period from 1212 midnight to 1212 noon is called 'a.m.' (ante meridiem), and the period from 1212 noon to 1212 midnight is called 'p.m.' (post meridiem). Think of a horizontal timeline split exactly in the middle at the noon sun position.

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The 24-hour Clock: Used frequently in railways and airlines, this format counts hours from 00:0000:00 to 23:5923:59. To convert a p.m. time to the 2424-hour format, you add 1212 to the hours. For example, 4:004:00 p.m. is viewed as 4+12=16:004 + 12 = 16:00 hours on a continuous digital display.

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Relationship between Days and Years: A standard year has 365365 days, while a Leap Year has 366366 days. A leap year occurs every 44 years when the month of February has 2929 days instead of 2828. Picture a calendar grid where an extra day is added at the end of the second month.

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Minutes and Seconds: 11 minute is equal to 6060 seconds. When converting minutes to seconds, we multiply the number of minutes by 6060. If we have seconds and want minutes, we divide by 6060 and the remainder represents the leftover seconds.

📐Formulae

1 minute=60 seconds1 \text{ minute} = 60 \text{ seconds}

1 hour=60 minutes=3600 seconds1 \text{ hour} = 60 \text{ minutes} = 3600 \text{ seconds}

1 day=24 hours1 \text{ day} = 24 \text{ hours}

1 week=7 days1 \text{ week} = 7 \text{ days}

1 year=12 months=365 days1 \text{ year} = 12 \text{ months} = 365 \text{ days}

Time in minutes=Time in hours×60\text{Time in minutes} = \text{Time in hours} \times 60

Time in seconds=Time in minutes×60\text{Time in seconds} = \text{Time in minutes} \times 60

Time in hours=Time in minutes60\text{Time in hours} = \frac{\text{Time in minutes}}{60}

💡Examples

Problem 1:

Convert 55 hours and 4545 minutes into minutes.

Solution:

Step 1: We know that 1 hour=60 minutes1 \text{ hour} = 60 \text{ minutes}. \ Step 2: Multiply the hours by 6060: 5×60=300 minutes5 \times 60 = 300 \text{ minutes}. \ Step 3: Add the remaining minutes: 300+45=345 minutes300 + 45 = 345 \text{ minutes}. \ Therefore, 5 hours 45 minutes=345 minutes5 \text{ hours } 45 \text{ minutes} = 345 \text{ minutes}.

Explanation:

First, we convert the larger unit (hours) to the smaller unit (minutes) using multiplication, then we add the extra minutes already given in the problem.

Problem 2:

Convert 200200 seconds into minutes and seconds.

Solution:

Step 1: We know that 60 seconds=1 minute60 \text{ seconds} = 1 \text{ minute}. \ Step 2: Divide 200200 by 6060: 200÷60200 \div 60 \ Step 3: 60×3=18060 \times 3 = 180. Subtracting 180180 from 200200 gives a remainder of 2020. \ Quotient =3 minutes= 3 \text{ minutes}, Remainder =20 seconds= 20 \text{ seconds}. \ Therefore, 200 seconds=3 minutes and 20 seconds200 \text{ seconds} = 3 \text{ minutes and } 20 \text{ seconds}.

Explanation:

To convert from a smaller unit (seconds) to a larger unit (minutes), we divide by the conversion factor 6060. The quotient gives the full minutes and the remainder gives the remaining seconds.