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Middle School Math
Math

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 1 A chemistry experiment requires a salt solution. You have just dissolved 2.8 g of NaCl (salt) in 140 g of water. What is the final concentration (in g/ml) of your salt solution? Round your answer to the nearest thousandth.
 2 There is a rift about 12 km west of Seaside. Scientists have been measuring the depth of the rift for over a decade now and report that it gets deeper by an average of 8.4 cm per year. If the rift was 6.9 cm deeper last year, by what percent did the depth change differ from the annual average? Round your answer to the nearest hundredth.
 3 Four cross sections of petrified wood are measured. Their average diameter is 18.6 cm. Three specimens' actual diameters are 15.4, 15.4, and 16.4 cm. What must the diameter of the other specimen be?
 4 You do an experiment to collect data on earthworm behavior. You test the hypothesis that "If a worm is put into a terrarium, it will begin to bury itself within 10 seconds." After analyzing the data you report that the probability that a worm will begin to bury itself within 10 seconds is 0.8. Based on this information, what is the probability that the next two worms in a row will "bury within 10 seconds?"
 5 The momentum (in kg m/s) of an object depends on the object's mass and velocity (momentum = mass times velocity). Suppose you are a goalkeeper on a soccer team. The ball comes at you with a velocity 17 m/s. If the ball has a mass of 1,562 grams, what is the momentum of the ball when it strikes your hand as you deflect it from the goal in an incredible diving save?_________ kg m/s
 6 A class grew 50 carrots in sand and 50 in clay. After 6 weeks of growth they compared the plants to see which soil condition allowed the most root growth. The 50 from the sand had a total mass of 20 g and the 45 from the clay (5 died) had a mass of 18.7 g. What was the average root mass per plant from each of the experimental groups? Round your answer to the nearest thousandth of a gram.