SOLUTION: Kina solved -15q<135 by adding 15 to each side of the inequality. What mistake did she make? B. kina's solution was q<150. She checked her work by substituting 150 for q in the or

Algebra ->  Inequalities -> SOLUTION: Kina solved -15q<135 by adding 15 to each side of the inequality. What mistake did she make? B. kina's solution was q<150. She checked her work by substituting 150 for q in the or      Log On


   



Question 26350: Kina solved -15q<135 by adding 15 to each side of the inequality. What mistake did she make?
B. kina's solution was q<150. She checked her work by substituting 150 for q in the original inequality. Why didn’t her check let her know that she had made a mistake?

Found 2 solutions by queenofit, Earlsdon:
Answer by queenofit(120) About Me  (Show Source):
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First of all, Kina should not have added 15 to anything, she would have had to divided both sides of the equation by -15. The -15 is multiplied to the q not subracted.
when she checked her answer it gave her a number that was less than 135 so she thought that she was correct, but she was not.

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
First, Kina tried to add un-like terms (-15q+15) does not equal q, it equals (-15q+15). When she used 150 to check her solution, it would appear to have checked out because she would have ended up with: -2250<135 and this is true.
What Kina should have done is divide both sides of the inequality by -15 and, in doing this, she also should have reversed the order of the inequality.
-15q+%3C+135 Divide both sides by -15 and reverse the order of the inequality.
q+%3E+-9
To check her solution, Kina should try a number that is greater than -9 because her solution is the set of all numbers greater than -9.
Try -5:
-15%28-5%29+=+75
75+%3C+135 It checks!