SAT 10 Test 4 Math 11-15

​The mean is the average of the numbers. Add them up and divided by the number of values to get the mean.

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​The standard deviation is how spread out the numbers are. It almost like the range.

Let x represent the original price of the book.

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Then, 40% off of x is (1 − 0.40)x, or 0.60x.

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Since the sale price is $18.00, then 0.60x = 18.

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Dividing both sides of this equation by 0.60 yields x = 30.

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Therefore, the original price of the book was $30.​

​Three colonies of insects were each treated with a different pesticide over an 8-week period to test the effectiveness of the three pesticides. Colonies A, B, and C were treated with Pesticides A, B, and C, respectively. Each pesticide was applied every 2 weeks to one of the three colonies over the 8-week period. The bar graph shows the insect counts for each of the three colonies 0, 2, 4, 6, and 8 weeks after the initial treatment.

According to the bar graph, the number of insects in colony A at​ week 0 was approximately 80, and this number decreased over each respective two-week period to approximately 50, 32, 25, and 18. Similarly, the graph shows that the number of insects in colony B at week 0 was approximately 64, and this number also decreased over each respective two-week period to approximately 60, 40, 38, and 10. Finally, the graph shows that the number of insects in colony C at week 0 was approximately 58; however, the number of insects increased in week 2, to approximately 140. Therefore, only colony A and colony B showed a decrease in size every two weeks after the initial treatment.

​According to the bar graph, the total number of insects in all three colonies in week 8 was approximately 20 + 10 + 50 = 80, and the total number of insects at the time of initial treatment (week 0) was approximately 80 + 65 + 55 = 200. The ratio of these approximations is 80 to 200, which is equivalent to 2 to 5.