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Math Help - Writing inequality

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    Writing inequality

    1. Sam must have an average of 70 or more in his summer course to obtain a grade of C. His first three test grades were 75, 63, and 68. Write a inequality representing the score that Sam must get on the last test to get a C grade.







    2. The cost for a long-distance telephone call is $0.36 for the first minute and $0.21 for each additional minute or portion thereof. Write an inequality representing the number of minutes a person could talk without exceeding $3.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Patience View Post
    1. Sam must have an average of 70 or more in his summer course to obtain a grade of C. His first three test grades were 75, 63, and 68. Write a inequality representing the score that Sam must get on the last test to get a C grade.







    2. The cost for a long-distance telephone call is $0.36 for the first minute and $0.21 for each additional minute or portion thereof. Write an inequality representing the number of minutes a person could talk without exceeding $3.
    1. Sam must have an average of 70 or more in his summer course to obtain a grade of C. His first three test grades were 75, 63, and 68. Write a inequality representing the score that Sam must get on the last test to get a C grade.

    so you know the formula for average here would be (testscore1 + testscore2 + testscore3 + testscore4)/4

    the scores for the first three are given, we have to find the last using an inequility. since we want the average to be at least 70 to get a C, we have:

    Let the final score Sam needs for a C be x

    then (75 + 63 + 68 + x)/4 >= 70
    => 206 + x >= 280
    so x >= 74

    so Sam's final score has to be at least 74 to get a C (or above) according to the above inequality.

    2. The cost for a long-distance telephone call is $0.36 for the first minute and $0.21 for each additional minute or portion thereof. Write an inequality representing the number of minutes a person could talk without exceeding $3.

    Let x be the additional minutes we can talk for to not exceed a $3 bill. So the total number of minutes we can talk without exceeding $3 is x+1 minutes.

    we want 0.36 + 0.21x <= 3
    => 0.21x <= 2.64
    => x <=2.64/.21
    => x <= 12.57

    so if y is the total number of minutes we can talk
    y <= x + 1
    => y <= 13.57
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