Day 7 - Class Practice Key
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School
North Carolina State University *
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Course
450
Subject
Mathematics
Date
Feb 20, 2024
Type
Pages
2
Uploaded by Hi4235
g A survey found the mean length of time that Americans keep their cars is 5.3 years with a standard deviation of 1.2 years. If a person decides to purchase a new car, find the age below which 10% of car owners fall. — 2 8 = ¥X- 5 .2 Z_;—_—l.ZS —_— |- 2 *4[/\ —1.930C = ¥-5.3 [X="3776] 2. The average waiting time at Walgreens drive-through is 7.6 minutes with a standard deviation of 2.6 minutes. Find the middle 50% of times that customers can expect to Honors Math 4 - Working Backward Using Table A Practice 1. Wa“--jfi‘(s_o\!'\l?’_ — 0L15= X-T1-6 Ol 75= ¥X—1-b Z= 1 0.6715 “ e £l ~1.7155= X - Tl L7555 = ¥-715 E-‘35°>C] [G-20=x 3. A weight loss clinic guarantees that its new customers will lose at least 5 Ibs by the end of their first month of participation or their money will be refunded. If the data is normally distributed with an average loss of 6.7 Ibs and a standard deviation of 0.81 Ibs, find the amount of weight above which the top 12% of people lost. .88 |3 [.ITTS = X—= (b1 .81 A52 = X — (1 §7b5=fi ’ 4. You enter a fishing contest. The contest takes place in a pond where the fish lengths have a normal distribution with mean 16 inches and standard deviation 4 inches. Find the middle 60% of all fish lengths. + %2 b = - 8 LP ~.8d= X —1( +'84°’-§q_i‘—’- e (Dj;“a 3-56 =X~ -3 I_ifq~3(0=')<,J
5. Heights of kindergarten children are normally distributed with a mean of 40 inches and standard deviation of 6 inches. Find the fi;-gercentile of heights. 2272 (@2 —4.L2 =\ —40 [X= 35.3¢" 6. The scores on an Algebra |l test have a mean of 76.4 and a standard deviation of 11.4. If the top 5% of students are given an award, find the score above which they must score. fl‘s\[\. 1.4S = X - T6.Y (-4 }K‘-QCS-IS 7. The average life of automobile tires has a mean of 30,000 miles with a standard deviation of 2000 miles. A warranty is issued that provides new tires for those tires whose lives fall below the 15th percentile. What is the lifetime below which consumers will qualify for new tires? —E —1.04= X~30000 2000 -2080 = (- 30000 8. The mean height of an American man is normally distributed with a mean of 69" and a standard deviation of 2.4”. Find the height above which the top 2% of men fall. _ ) 2 4 3272 = ¥-0,9
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