In grade four, new concepts are introduced in math. Some new concepts are time, multiples and factors, addition and subtraction of three digit numbers, unitary method, measures of length, mass and capacity, fractional numbers, addition and subtraction of fractions, decimals, addition and subtraction of decimals, Introduction to angles.
Introduction to grade four math:
In grade four, the topic time contains the following sub units.
- Measurement of time
-Calender
- Time in second
- Addition and subtraction of time
In this article let us learn about 24-hour clock time.
In the present day world business houses, airlines, railways are busy round the clock. Hence it is convenient to use 24 - hour time representation instead of a.m. and p.m.
1. 12 O' clock midnight is expressed as 00 00 or 24 00
2. 12 O' clock is expressed as 12 00
3. The time between 12 O' clock noon and 12 O' clock midnight is expressed by adding 12 hours to the given hours period.
For example:
25 minutes past 6 in the evening is expressed as 18 25
45 minutes past 11 midnight is written as 23 45
Rules for Writing 24-hour Clock Time:
A day begins at 12 midnight (00:00 hours) and hence at 12 midnight the following day.
Thus 1 day = 24 hours
Rule 1: For any time in a.m. we simply put down the time by writing hours and minutes in two digits numbers.
Rule 2: For any time written in p.m. we simply add 12 hours to the number of hours period and write minutes without separating them.
6:25 a.m is written as 06 25 hours
10:45 a.m is written as 10 45 hours
3:10 p.m. is written as 15 10 hours (3 + 12 = 15)
10:50 p.m. is written as 22 50 hours (10 + 12 = 22)
Example Problems on Grade Fourth Math:
Ex 1: Express 11:25 p.m. in the 24 hours system.
Sol:
Step 1: See which rule can be used.
Step 2: Since the time given is in p.m., add 12 to 11
Step 3: So, 11:25 p.m. = (11 + 12 hours) : 25 min
= 23 25 hours
Ex 2: Express 18 30 hours in terms of a.m. or p.m.
Sol:
18 30 hours means (12 + 6 hours) 30 minutes
= 6:30 p.m.
Ex 3: Express 07:45 p.m. in the 24 hours system.
Sol:
Step 1: See which rule can be used.
Step 2: Since the time given is in p.m., add 12 to 7
Step 3: So, 07:45 p.m. = (7 + 12 hours) : 45 min
= 19 : 45 hours
Introduction to grade four math:
In grade four, the topic time contains the following sub units.
- Measurement of time
-Calender
- Time in second
- Addition and subtraction of time
In this article let us learn about 24-hour clock time.
In the present day world business houses, airlines, railways are busy round the clock. Hence it is convenient to use 24 - hour time representation instead of a.m. and p.m.
1. 12 O' clock midnight is expressed as 00 00 or 24 00
2. 12 O' clock is expressed as 12 00
3. The time between 12 O' clock noon and 12 O' clock midnight is expressed by adding 12 hours to the given hours period.
For example:
25 minutes past 6 in the evening is expressed as 18 25
45 minutes past 11 midnight is written as 23 45
Rules for Writing 24-hour Clock Time:
A day begins at 12 midnight (00:00 hours) and hence at 12 midnight the following day.
Thus 1 day = 24 hours
Rule 1: For any time in a.m. we simply put down the time by writing hours and minutes in two digits numbers.
Rule 2: For any time written in p.m. we simply add 12 hours to the number of hours period and write minutes without separating them.
6:25 a.m is written as 06 25 hours
10:45 a.m is written as 10 45 hours
3:10 p.m. is written as 15 10 hours (3 + 12 = 15)
10:50 p.m. is written as 22 50 hours (10 + 12 = 22)
Example Problems on Grade Fourth Math:
Ex 1: Express 11:25 p.m. in the 24 hours system.
Sol:
Step 1: See which rule can be used.
Step 2: Since the time given is in p.m., add 12 to 11
Step 3: So, 11:25 p.m. = (11 + 12 hours) : 25 min
= 23 25 hours
Ex 2: Express 18 30 hours in terms of a.m. or p.m.
Sol:
18 30 hours means (12 + 6 hours) 30 minutes
= 6:30 p.m.
Ex 3: Express 07:45 p.m. in the 24 hours system.
Sol:
Step 1: See which rule can be used.
Step 2: Since the time given is in p.m., add 12 to 7
Step 3: So, 07:45 p.m. = (7 + 12 hours) : 45 min
= 19 : 45 hours
