Wednesday, July 13, 2011

Practice for the quiz on Thursday 7/14: polygons and time

The sum of the interior angles of a polygon with n sides is (n – 2)180 °. Use this formula in the following problems.

a) What is the sum of the interior angles of a 10-sided polygon (decagon)?

b)If the interior angles of a polygon add up to 1260 °, how many sides does it have?

The angle measure of a regular n-sided polygon is (180 - 360/n) °.

c) What is the angle measure of a regular 10-sided polygon (decagon)?

d) If the angle measure of a regular polygon is 170°, how many sides does it have?

time problems.

e) How many minutes in 5 days?

f) 510 hours is __________ days and ________ hours.

g) 6,502 seconds is ________ hours, ________ minutes and __________ seconds.

h) 6,502 hours is ________ weeks, ________days and __________ hours.

i) After a flu outbreak, a hospital has decided quarantine will last 66 hours. If it starts at 5:00 pm on Tuesday, give the day and time when it will be over.

Day: ________ time: ___________ a.m or p.m? __________

Prof. Hubbard said...

The sum of the interior angles of a polygon with n sides is (n – 2)180 °. Use this formula in the following problems.

a) What is the sum of the interior angles of a 10-sided polygon (decagon)?

(10-2)*180 = 8 * 180 = 1440°

b)If the interior angles of a polygon add up to 1260°, how many sides does it have?

(n - 2)180 = 1260
180n - 360 = 1260
180n = 1620
n = 1620/180 = 9 sides.

The angle measure of a regular n-sided polygon is (180 - 360/n)°.

c) What is the angle measure of a regular 10-sided polygon (decagon)?

180 - 360/10 = 180 - 36 = 144°

d) If the angle measure of a regular polygon is 170°, how many sides does it have?

180 - 360/n = 170
10 - 360/n = 0
10 = 360/n
10n = 360
n = 36

time problems.

e) How many minutes in 5 days?

f) 510 hours is __________ days and ________ hours.

510/24 = 21 1/4
1/4 of a day is 6 hours, so 510 hours is 21 days and 6 hours.

g) 6,502 seconds is ________ hours, ________ minutes and __________ seconds.

6502 seconds is 108 minutes and 22 seconds
108 minutes is 1 hour and 48 minutes.

6,502 seconds is 1 hour, 48 minutes and 22 seconds.

h) 6,502 hours is ________ weeks, ________days and __________ hours.

6502 hours is 270 days and 22 hours.
270 days is 38 weeks and 4 days.

6,502 hours is 38 weeks, 4 days and 22 hours.

i) After a flu outbreak, a hospital has decided quarantine will last 66 hours. If it starts at 5:00 pm on Tuesday, give the day and time when it will be over.

66/24 is 2 days and 18 hours.

Two days after Tuesday is Thursday. 18 hours after 5:00 pm is 11:00 am the next day, so the quarantine ends 11:00 am on Friday.

Prof. Hubbard said...