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# \$7.50word problems

• From Mathematics: Algebra
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• Due on Oct. 28, 2007
• Asked on Oct 21, 2007 at 3:28:43PM

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1. A shipment contains x film cartridges for 15 exposures each and x + 10 cartridges for 25 exposures each. What is the total number of photographs that can be taken with the film from this shipment?

2. Each of two stores has 2n+ 1 mouse pads costing \$3 each and n-2 pads costing \$2 each. How much more is the total value of the \$3 mouse pads than the \$2 mouse pads in the two stores.

3. A person 1.8 m tall is photographed with a 35-mm camera, and the film image is 20mm. Under the same conditions, how tall is a person whose film image is 16mm?

4. In testing the rate at which a polluted stream flows, a boat travels at 5.5 mi/h in still water took 5.0 h to go downstream between points, and it took 8.0 h to go upstream between the same two points. What is the rate of flow of the stream.

5. An air sample contains 4.0 ppm(parts per million) of two pollutants. The concentration of one is four times the other. What are the concentrations.

6. a 5.0 piece of tubing weighs 1.7lb. What is the weight of a 27-ft piece of the same tubing.

7. A ship enters the red sea from the suez canal, moving south 17.4 mi/h. Two hours later, a second ship enters the Red Sea and the southern end, moving north at 21.8 mi/h. If the red sea is 1390 long. When will the ships pass?

8. Fifty pounds of cement sand mixture is 40% sand. How many pounds of sand must be added for the resulting mixture to be 60% sand?

9. a karat equals 1/24 part of gold in an alloy(for ex. a 9-karat gold is 9/24 gold). How many grams of 9-karat gold must be mixed with 18-karat gold to get 200g of 14-karat gold?

10. An alloy weighing 20lb is 30% copper. How many pounds of another alloy, which is 80% copper must be added for the final alloy to be 60% copper?

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• Posted on Oct 21, 2007 at 8:34:06PM
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Preview: ... * t<br><br>t = 1355.2/39.2 = 34.57 hours<br><br>You should check why this is true. If you replace this value for t in the first equation, d = 21.8 * t, you will see that d equals 753.63 miles.<br><br>If you do this for the other boat, you will see that the distance it travels in 34.57 hours equals 601.52 miles (d = 17.4 * t; 601.52 = 17.4 * 34.57). If you sum to that the distance travelled initially during those 2 hours, 34.8 miles, you get 636.32 miles. When you subtract this from the length of the Suez canal, which is 1390, you get 753.68 miles, which is approximately the distance travelled by the first boat, thus confirming our result. This problem was a bit tricky. I hope you managed to understand it.<br><br>8.<br><br>50 pounds is the total weight of the mixture and 40% of it is sand, so the total weight of sand in the mixture is 50 * 0.4 = 20 pounds. Now, we need the fraction of sand to be 60% of the total mixture, so we can write the equation:<br><br>(20 + x) / (50 + x) = 0.6<br><br>The numerator represents the weight of sand in the mixture, x being the amount added after, and the denominator, the total weight of the mixture, being x the extra weight of sand added. We rearrange the equation:<br><br>20 + x = 0.6* (50 + x)<br><br>20 + x = 30 + 0.6x<br><br>x - 0.6x = 30 - 20 <br><br>0.4x = 10<br><br>x = 25<br><br>This means we need to add an extra 25 pounds of sand to the mixture. You can confirm this by doing 20 + 25 (this is sand) divided by 50 + 25 (total components). This equals 60%<br><br>9.<br><br>The formula of the karat is x = 24 * Mg/Mt, where x is the karat rating, Mg the mass of pure gold and Mt the total mass of the sample. So, 200g of 14-karat gold means that its total mass is 200g.<br><br>14 = 24 * Mg/200<br><br>Mg = 200*14/24 ...

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