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#1
Sep 8 2013 08:00am
I need help doing some exercises for homework. I am really rusty with my calc since it has been 2 years since I have taken it and have no memory of the class

1.2
A length of concrete pavement requires 6 bags of portland cement per cubic yard of concrete.
How many pounds of portland cement are required for a mile of pavement? there are 94 pounds of cement in a bad,
and the width of the pavement is 24ft, the depth is 10 inches (cement is the stuff that holds concrete together)
Correct units is important

1.3
A dam on the outlet of Moosehead lake that feeds the Kennebec river releases 110 cubic meters of water per second
for a period of one day. How much would the level of the lake fall during that day if there were no other water
entering the or leaving the lake? the area of Moosehead lake is 310 square kilometers.
Units is important

1.4
You have a half acre lawn to cut using a lawn mower with a 20 inch base (i.e it cuts a 20 inch wide path).
Roughly how many miles would you have walked when you are done? excluse lemonade breaks


I don't have fg on me atm but if you will do it for fg I can probably get about 50-100 fg in like 2 minutes.
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#2
Sep 8 2013 09:08am
will pay 150, i have rp cards that sell for like 2kfg each instantly


This post was edited by Elements_Fury on Sep 8 2013 09:08am
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#3
Sep 8 2013 09:34am
Quote (Elements_Fury @ 8 Sep 2013 14:00)
I need help doing some exercises for homework. I am really rusty with my calc since it has been 2 years since I have taken it and have no memory of the class

1.2
A length of concrete pavement requires 6 bags of portland cement per cubic yard of concrete.
How many pounds of portland cement are required for a mile of pavement? there are 94 pounds of cement in a bad,
and the width of the pavement is 24ft, the depth is 10 inches (cement is the stuff that holds concrete together)
Correct units is important

let's list the units involved:

cubic yard = 27 cubic feet
mile = 5,280 feet
foot = 12 inches ie 10 inches = 5/6 foot

the volume of one mile of pavement is: (1 mile) * (24 ft) * (10 inches) = (5,280 ft) * (24 ft) * (5/6 ft) = 5,280 * 24 * 5/6 cubic feet = 5,280 * 20 cubic feet = 10,560 cubic feet
6 bags = 6 * 94 pounds = 564 pounds
564 pounds per cubic yard is 564 pounds for 27 cubic feet, ie one needs 188 / 9 pounds per cubic foot
so one needs (188/9) * 10560 pounds = 220,586 + 2/3 pounds

1.3
A dam on the outlet of Moosehead lake that feeds the Kennebec river releases 110 cubic meters of water per second
for a period of one day. How much would the level of the lake fall during that day if there were no other water
entering the or leaving the lake? the area of Moosehead lake is 310 square kilometers.
Units is important

metric is far easier  :D

a day has 60 * 60 * 24 seconds = 86,400 seconds
ie the daily release of water is 86,400 * 110 cubic meters = 9,504,000 cubic meters
now a square kilometer has 1,000 * 1,000 square meters, ie the surface area is 310,000,000 square meters
now if you divide the volume by the area your result is the depth in meters
9,504,000 / 310,000,000 = 0.030657064.... meters or 3.07 (rounded) centimeters or ~1.2 inches

1.4
You have a half acre lawn to cut using a lawn mower with a 20 inch base (i.e it cuts a 20 inch wide path).
Roughly how many miles would you have walked when you are done? excluse lemonade breaks


I don't have fg on me atm but if you will do it for fg I can probably get about 50-100 fg in like 2 minutes.


now an acre = 43,560 square feet and with a square foot being 144 square inches we have 6,272,640 square inches
if we divide this by 20 we have a strip 20 inches wide and 313,632 inches long, divide by 12 and the strip is 26,136 feet long (for one acre)
now half it to get the length of the strip for half an acre, ie 13,068 feet long
dividing this by 5,280 (the number of feet in the mile) gives 2.475 miles, so roughly 2 1/2 miles
(this is ignoring the shape of the lawn and the amount of walking needed to turn)

ensure you go through the steps, understand them and verify the calculations (for all three)

This post was edited by brmv on Sep 8 2013 09:48am
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#4
Sep 8 2013 12:41pm
564 pounds per cubic yard is 564 pounds for 27 cubic feet, ie one needs 188 / 9 pounds per cubic foot
so one needs (188/9) * 10560 pounds = 220,586 + 2/3 pounds

I got lost here
where is the 188/9 from?
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#5
Sep 8 2013 12:43pm
Quote (Elements_Fury @ Sep 8 2013 11:41am)
564 pounds per cubic yard is 564 pounds for 27 cubic feet, ie one needs 188 / 9 pounds per cubic foot
so one needs (188/9) * 10560 pounds = 220,586 + 2/3 pounds

I got lost here
where is the 188/9 from?


564/27 divided by 3 i think

This post was edited by khemist on Sep 8 2013 12:44pm
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#6
Sep 8 2013 05:50pm
Quote (Elements_Fury @ 8 Sep 2013 18:41)
564 pounds per cubic yard is 564 pounds for 27 cubic feet, ie one needs 188 / 9 pounds per cubic foot
so one needs (188/9) * 10560 pounds = 220,586 + 2/3 pounds
I got lost here
where is the 188/9 from?


564/3=188 and 27/3=9, easier to use the fraction 188/9 than the decimal equivalent 20.88888888...., so

Quote (khemist @ 8 Sep 2013 18:43)
564/27 divided by 3 i think


this is right
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