## Arithmetic Chapter 12 Measurement Of Time

**Arithmetic Chapter 12 Different units of measurement of time**

**1.**

**Day:**The time is taken by the Earth to make one complete rotation around- its own axis is called one day.
**Hour:**If one day is divided into 24 equal parts, then each part is called one- hour.
**Minute:**When one hour is divided into 60 equal parts, then one part is called one minute.**Second:**When one minute is divided into 60 equal parts, then one part is called one second.- So 1 day = 24 hours
- 1 hour = 60 minutes

1 minute = 60 seconds

**2.**

**Week:**7 days make one week.**Date:**7 days in a week are denoted by 7 dates.- The dates are
- Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

and Sunday. **Fortnight:**2 weeks together is called a Fortnight. In Bengali 15 days together are called a Fortnight.- The number of fortnights two

1. The bright fortnight (Sukla fortnight)

2. The dark fortnight (Krishna Fortnight). **Month:**Generally a month is said to have 30 days, although all the months of a year do not have 30 days.- The total number of days in different months is given below
- January = 31 days

February = 28 days (In a leap-year, the month of February will have 29 days)

March = 31 days

April = 30 days

May = 31 days

June = 30 days

July = 31 days

August = 31 days

September = 30 days

October = 31 days

November = 30 days

December = 31 days. **Year:**Usually a year contains 12 months or 365 days.- But a Leap-Year contains 366 days.
years altogether is called**A period: of 12****a period.**- So, 7 days = 1 week 1 Fortnight (Paksha) = 2 weeks (In Bengali 15 days)

1 month = 30 days

1 year = 365 days (General year) = 366 days (Leap-year)

1 month = 2 Fortnights

1 year =12 months

1 period (Years) =12 years

1 century =100 years. : If the number denoting a year is divisible by 4, then the year is known as**Leap-year****Leap-year.**1908, 1912, and 1916, years, etc. are Leap years,**For example**- A leap year has 366 days and the month of February has 29 days.
- But all the years denoting the century are not leap years.
**A century year will be a leap year if the number denoting the year is divisible by 400.**- The years
are leap years as these numbers are divisible by**1624, 1736, 1984, and 2004****4.** - Again the century years
are leap-years as these numbers are divisible by**1600, 2000, and 1200**whereas the century years**400**are not leap-years as they are not divisible by**1700, 1800, and 1900****400.** :**Century-year**years altogether is known as a**100****Century year.**- For example Nineteenth century (from
year to**1801**year)**1900** - The Twentieth century (From
year to**1901.**year)**2000** - Twenty oneth century (From
year to 2100 year) etc.**2001**

## Arithmetic Chapter 12 Addition, Subtraction Multiplication and Division in the Measurement of Time

- In our daily life, sometimes we are to do addition, subtraction, multiplication, and division two or more times.
- In this regard, we shall discuss illustrative examples.
- In general, following the rules discussed below, we add, subtract, multiply, and divide the problems regarding times.
In the case of a second or minute**Rule 1.**is taken as a unit; i.e., in two or more mathematical operations about seconds or minutes which are more than**60**seconds or**60**minutes, then we write the remaining seconds or minutes taking every**60**seconds or**60**minutes as units.**60**- For example,
seconds +**52**seconds =**44**seconds. We take**96**seconds =**60**minute, so there is the remaining**1**seconds.**96 – 60 = 36** - ∴ The addition can be written as
seconds +**52**seconds =**44**minute**1**seconds.**36** In the case of hours and days, 24 hours is taken as a unit i.e., 24 hours = 1 day.**Rule 2.**In the case of days and weeks, 7 days are taken as a unit, i.e., 7 days = 1 week.**Rule 3.**In the case of weeks and years, 52 weeks is taken as the unit, i.e., 52 weeks = 1 year.**Rule 4.**In the case of days and months, 30 days are taken as a unit, i.e., 30 days = 1 month.**Rule 5.**In the case of days and years, 365 days are taken as a unit, i.e., 365 days = 1 year.**Rule 6.**In the case of months and years, 12 months is taken as a unit, i.e., 12 months = 1 year.**Rule 7.**In the case of years and periods, 12 years is taken as a unit, i.e., 12 years = 1 period.**Rule 8.**

## Arithmetic Chapter 12 Day of a particular date

- If we know the day of a particular date of any year, then we can easily calculate the day of any date preceding or following year.
- First, we shall calculate the number of days between the two given dates
of these two given dates.**including only one day** - Then divide the number of days by 7.
- If there is no remainder, then the day of the required date will be the same day as the given date.
- If the remainder is 1, then the day of the required date will be the first day after or before the given day in the case of the following year or the preceding year.
- Again if the remainder is 2, then the day of the required date will be the second day after or before the given day in case of the following or preceding year and so on.