Writing an inequality

jakezepre

New member
Joined
Dec 15, 2010
Messages
4
The question: You earned the following scores on 4 math tests: 88, 86, 92 and 84. You want to have an average of at least 85 after you take the 5th test. Write and solve an inequality to find the possible scores that you can earn on the 5th test in order to meet your goal.

I know that I need to have at least a 75 on my 5th test in order to have an average of 85. I tought that (x + 350) / 5 is greater than or equal to 85 BUT taht would not give me the correct answer because if I put in 0 for x I wouldn't have more than 75. I think that I should do 85 times 5 which is 425. Then (x + 425)/5 is greater than or equal to 85? Is that correct???
 
jakezepre said:
The question: You earned the following scores on 4 math tests: 88, 86, 92 and 84. You want to have an average of at least 85 after you take the 5th test. Write and solve an inequality to find the possible scores that you can earn on the 5th test in order to meet your goal.

I know that I need to have at least a 75 on my 5th test in order to have an average of 85. I tought that (x + 350) / 5 is greater than or equal to 85 BUT taht would not give me the correct answer because if I put in 0 for x I wouldn't have more than 75. I think that I should do 85 times 5 which is 425. Then (x + 425)/5 is greater than or equal to 85? Is that correct???

88 + 86 + 92 + 84 = 350

(350+x)/5 ? 85
 
Thank you, but what I don't understand or know how to do is to solve the inequality, I know that X has to be greater than or equal to 75. But i don't know how to get there..Please help!
 
Subhotosh Khan said:
jakezepre said:
The question: You earned the following scores on 4 math tests: 88, 86, 92 and 84. You want to have an average of at least 85 after you take the 5th test. Write and solve an inequality to find the possible scores that you can earn on the 5th test in order to meet your goal.

I know that I need to have at least a 75 on my 5th test in order to have an average of 85. I tought that (x + 350) / 5 is greater than or equal to 85 BUT taht would not give me the correct answer because if I put in 0 for x I wouldn't have more than 75. I think that I should do 85 times 5 which is 425. Then (x + 425)/5 is greater than or equal to 85? Is that correct???

88 + 86 + 92 + 84 = 350

(350+x)/5 ? 85

(350+x)/5 * 5 ? 85 * 5

(350+x) ? 425

350 + x - 350 ? 425 -350

x ? 75
 
Top