A student is solving the following problem: Cody is 44 years younger than Kathryn. 7 years ago, Kathryn's age was 3 times Cody's age. How old is Kathryn now? The student writes out his solution, noting what he did: Cody now = c, so Cody 7 years ago was c -7 Kathryn now = k, so Kathryn 7 years ago was k -7 Cody is 44 years younger than Kathryn, so c = 44 - k 7 years ago, Kathryn's age was 3 times Cody's age k-7 = 3(c - 7) k-7 = 3[44 - k - 7] Substitute for c using c = 44 - k k-7 = 3[-k + 37] Simplify k-7 = -3k + 111 4k = 118 k = 29.5 There is no way that Kathryn's age is 29.5 if Cody is supposed to be 44 years younger than Kathryn, so what went wrong? What mistake did the student make?

Bonnie runs 1(2)/(3) times as far as John each day. If Bonnie runs 5 miles on Monday, 3(1)/(2) miles on Tuesday, and 5(3)/(4) miles on Wednesday, how many miles did John run in all those three days?

Mrs. Jerry wants her 25 students to each have 12 buttons to make a craft project. Mrs. Jerry finds buttons in bags at a store. There are 15 buttons in each bag. How many bags of buttons does Mrs. Jerry need to buy so she has exactly enough buttons for her 25 students? Show all your mathematical thinking.

The owner of a golf course wants to determine if his golf course is more difficult than the one his friend owns. He has 26 golfers play a round of 18 holes on his golf course and records their scores. Later that week, he has the same 26 golfers play a round of golf on his friend's course and records their scores again. The average difference in the scores (treated as the scores on his course - the scores on his friend's course) is -1.79 strokes and the standard deviation of the differences is 5.907 strokes. The owner uses this information to calculate the 90% confidence paired t-interval of (-3.769, 0.189). Which statement is the correct interpretation of this interval?   Question 10 options:   1)  We are 90% confident that the difference between the average score on the owner's golf course and the average score on the friend's golf course is between -3.769 and 0.189.   2)  We are certain the average difference in scores between the two…

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Elliot had some red, blue and green pens for sale. There were 48 more blue pens than green pens. He had 10 more red pens than blue pens. After selling 3/4 of the blue pens and 1/2 of the green pens, there were 315 pens left. (a) How many green pens did Elliot have at first? (b) How many pens did Elliot have in total at first?

Shelley pours  gallon of water into a bird bath. The next morning, she finds that of the water is gone. What is the amount of water, in gallons, that is gone?

Ali, Ben and Calvin divided some stickers among themselves. Ali took 20 stickers and 1/5 of the remaining stickers. Next, Ben took 1/6 of the remaining stickers and 30 more. Finally Calvin took the 240 stickers that were left over. (a) How many stickers did Ben take? (b) How many stickers were there in total at first?

Jennifer had a total of 132 markers and crayons. After she gave away 4/5 of markers and 18 crayons, she had an equal number of markers and crayons left. (a) How many markers did she have left? (b) How many crayons did she have at first?