1. Your living room measures 25 ft by 15 feet. How many square yards of carpet do you need to cover the floor? If carpet (including installation) is $35 per square yards, how much will it cost?

2. How many feet of snow fence does it take to enclose an excavation 20 ft in diameter if the fence is located 4 ft from the perimeter of the hole?

3. Find the volume, in gallons of an 18-inch force main that is 2 miles long.

4. An 8-ft deep tank has a diameter of 10 feet. Will its contents fit into a 5,000 gallon tanker?

5. A rectangular primary clarifier is 75′ long, 22′ wide and 10′ swd. If it gets a flow of 1250000 gpd, what is the detention time in hrs?

Answers:

1. 41.67 sq yrds, $1,458.33

First find sqft – 25′ X 15′ = 375 sqft, now convert from feet to yards. There are 3 ft per yard so, (375 sqft) / (3 ft/yrd) 125 ft/yards, but we need square yards so we have to divide by 3 sqft/yrd again ((125 ft/yrds) / (3 ft/yrd) =

2. 88 ft

20 ft + 4 ft + 4 ft = 28 ft, and to find perimeter including the extra 4 ft set back = 3.14 X 28′ =

3. 139,514 gal

Change from inches to feet (18″) / (12″/ft) = 1.5 ft diameter, now find radius (1/2 of diameter) = (1.5′) / (2) = 0.75 ft. Volume, cuft formula = 3.14 X R’ X R’ X H’, but instead of H we will use length, but it is given in miles and we need feet so, there is 5280 ft per mile = 5280 ft/mile X 2 miles = 10560 ft, now complete formula = 3.14 X 0.75′ X 0.75′ X 10560 ft = 18651.6 cuft, but we need gallons – 18651.6 cuft X 7.48 gal/cuft =

4. Yes

Find cuft (volume) = (10 ft) / (2) = 5 ft X 5 ft X 3.14 X 8 ft = 628 cuft, now convert to gallons using 7.48 gal/cuft = 628 cuft X 7.48 gal/cuft = 4697.44 gal

5. 2.37 hrs

Detention time, hrs = (Volume) / (Flow Rate) – The key is to keep your units straight – if the VOLUME is in GAL keep the FLOW in GAL, if the VOLUME is in MG keep the FLOW in MGD

Find Volume, cuft = 75 ft X 22 ft X 10 ft = 16500 cuft, now convert to gallons =

16500 cuft X 7.48 gal/cuft = 123420 gal, now since the flow is given in gpd, convert your flow to gpd = 123420 gal X 24 hrs/day = 2962080 gal/day, now finish the formula =

(2962080 gal/day) / (1250000 gpd) =