1. Time
Every person’s life revolves around time. You wake up at a particular time every morning.
The day can be split into two halves. The day has 24 hours in it.
Midnight to midday: first 12 hours of the day: Called AM
Next 12 hours from noon back to midnight are called PM.
Time can be shown in two formats: 24-hour and 12-hour. Let us learn about these formats in the coming sections.
1.1 What is 24-hour clock?
It is more often shown on digital clock with the numbers 1-24. The time represented by 24-hour clock is in four digits, with the first two digits denoting the hours while the last two digits denoting the minutes.
AM or PM is not used in the 24-hour time format.
For example:
Six AM in the 24-hour clock will be 06:00.
Three-thirty PM in the 24-hour clock will be 15:30 (15 hours = 12 hours + 3 hours).
1.2 What is 12-hour clock?
It is more often shown on analogue clock with the numbers 1-12. The time represented by 12-hour clock is followed by AM or PM.
Examples: 3 am, 4 pm, 5:30 pm
2. Time Conversions
Time can be measured in seconds, minutes, hours, days, weeks, months and years.
Conversion time guide:
Normal year have 365 days while leap year have 366 days. Leap year happens every four years.
Let us now workout some examples on time conversions:
2.1 Time Conversion: Solved Examples
Convert:
a) 17 minutes 45 seconds to seconds.
Solution;
First step is to convert 17 minutes to seconds.
1 minute has 60 seconds.
17 minutes = 17×60 = 1020 seconds
So 17 minutes 45 seconds = 1020 seconds + 45 seconds
= 1065 seconds
b) 4 weeks 3 days 12 hours to hours
Solution:
First step is to convert 4 weeks to days and to hours.
One week has 7 days, so 4 weeks has
7×4=28 days
One day has 24 hours, so 28 days has
24×28 = 672 hours
Second step is to convert 3 days to hours
One day has 24 hours, so 3 days has
24×3 = 72 hours
Now 4 weeks 3 days 12 hours = 672 hours + 72 hours + 12 hours
= 756 hours
2.2 Time Loss and Gain
When the clock is running fast, time is gained and when is running slow, the time is lost.
Let us understand the terms time loss and gain using a simple example.
If a clock shows 7.20 when the correct time is 7.30, the clock is late by 10 minutes and it losses time.
If a clock shows 7.20 when the correct time is 7.10, the clock is fast by 10 minutes and it gains time.
Let us now learn how to workout the correct time given the time gain or loss with the example below.
Example: A clock gains 15 minutes in one hour and was set right at 11 AM. What time will this clock show at 3 PM on the same day?
Solution:
The clock gains 15 minutes in an hour.
Number of hours passed from 11 AM to 3 PM = 4
Time gained by the clock in 4 hours = 4×15 = 60 minutes
So after 4 hours i.e. at 3 PM, the clock will be 60 minutes or one hour ahead.
At 3 PM the clock will show 4PM.
3. Date Problems
Things to remember while solving date problems:
- Number of days in ordinary year = 365
- Number of days in leap year = 366
- Number of days in one month = 30 or 31
- Number of days in one week = 7
Let us now use this information and try to solve an example of date problem.
Example: If the 8th of June was Friday, what day was on 19th of September of the same year?
Solution:
One week has 7 days.
After every week the days will repeat.
The number of days from 8th June to 19th December = 103 days
And, 103⁄7=14R5
We have 14 full weeks and 5 days extra.
The 5th day after Friday is Wednesday.
19th September is a Wednesday.
