Answer to Question #106667 in Math for Riya

Question

Explain sexagesimal system used for operations on time. Give one example each of the problems involving subtraction and addition of time showing the error children make because of the sexagesimal system. How would you help children correct their error.

Answer 1

sexagesimal is a numerical system with sixty as its base .it originated with the ancient Sumerians in the third millennium is used in a modified way for measuring time.

an example of an addition problem

Express 85.12° in degree minute and second

1 minute85.12° = 85° + (0.12)°

= 85° + (0.12 × 60)’ [Since, 1° = 60’]

= 85° + 7.2’

= 85° + 7’ + (0.2)’

= 85° + 7’ + (0.2 × 60)”

= 85° + 7’ + 12”

Therefore, 85.12° = 85° 7’ 12”

Example of Subtraction

If we need to add 20 minutes to 1 hour 50 minutes, we will have 2 hours 10 minutes (NOT 1 hour 70 minutes, because we know that there's just 60 minutes in 1 hour). To simplify, we can draw 2 circles and split them into 6 equal parts for 10 minutes and use them for explanation. The same thing with subtraction, for example, given 3 hours 10 minutes and we need to subtract 1 hour 30 minutes. We come back to our circles (we have 4 circles divided by 6 parts each) There are 3 whole circles and 1 part of 4th painted. Return to 1 hour 30 minutes we can say that it is 1 whole circle 3 parts. So, we need just subtract 1 whole circle 3 parts(1 hour 30 minutes) from our painted parts in circles (3 hours 10 minutes).