Sara wrote:These may be simple, but I dont understand them. Please help.

1. Express 120 m/s in feet per second. (1.m =3.28 ft)

This is a simple conversion, as you've said. You know that you have 120 meters per second, you want feet per second. All you need to do is ignore the second, as they are the same on both sides, and convert meters to feet. Since you know that 1 meter is 3.28 feet and you have 120 meters, then all you need to do is multiply 120 meters by 3.28 feet per meter to get an answer in meters.

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` m 3.28 ft/m ft`

120 --- x = 393.6 ---

sec sec

Sara wrote:2. If each serving of coffee is 175ml, how many liters of coffee are needed to serve 80 people?

This one isn't even a conversion. Don't let the fact that it's in metric units scare you. Answer this: If each serving of coffee is one cup, and you need to serve 80 people, then how many cups of coffee do you need? The answer is, of course, 80. You multiplied one cup per serving by 80 servings, to get 80 cups. Now figure that the Coffee cup really holds six ounces... How much coffee? The same math: 6 ounce per serving times 80 servings is 480 ounces. Guess what? six ounces is about 175 ml. so:

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` ml`

175 ------- * 80 serving = 14,000 ml

serving

14,000 ml, is the same as 14 liters (one liter is 1,000 ml).

Sara wrote:3. How much fencing is required to enclose a play yard 10 m 80cm long and 4m 30 cm wide?

Again, don't get worried because the question talks about metric units. All you have to remember is how to manipulate the units. The prefix centi means 1/100th, so 100 cm is equal to 1 meter. Using this, you can figure out that 80 centimeters is 80/100ths of a meter, or 0.8 meters. So 10 m, 80 cm is 10.8 meters. Likewise 4 m, 30 cm is 4.3 meters. This means you want to find the perimeter of an area that is 10.8 meters long and 4.3 meters wide.

The formula for the perimeter of a rectangle is P=2L+2W So:

P = 2(10.8 m) + 2(4.3 m)

P = 21.6 m + 8.6 m

P = 30.2 meters

I hope this helps!

William J. Knight

Health Physicist

Los Alamos National Labs