184k views
2 votes
Todd has a collection of 8 CDs and Sally has a collection of 18 CDs. Todd is adding 9 CDs a month to his collection while Sally is adding 7 CDs a month to her collection. When will they have the same number of CDs and how many CDs will they have?

User Read Read
by
6.3k points

2 Answers

6 votes

Answer:

Explanation:

To solve this equation we will be using inequality's. The first thing you want to do is write both of these as linear equations. Todd- 9m+8 Sally-7m+18. M represents the amount of months, the number to the left M represents the amount of cds added per month, and the +18 and +8 represent the y intercept, also known as the starting value. We set both of these equations equal to each other, because we want to know when both equations are EQUAL to each other. 9m+8=7m+18. From here we solve by doing the following, we subtract 8 from each side to get 9m=7m+10, we then subtract 7m from 9m to get 2m=10, lastly we divide 2 from both sides to isolate m and get m=5. This means it would take five months for both of their CD counts to be even. To find how many we have, we simply put the value of m=5 into m. 9(5)+8, gives us 53. Meaning that they have 53 CDs and are equal at the fifth month.

User Dalin Huang
by
6.4k points
1 vote

todd = 8 + 9

sally = 18 + 7

Just keep adding until they have the same amount if they ever do.

todd 17 26 35 44 53

sally 25 32 39 46 53


so it took them 5 mouths and they both have 53 CD's

User Comte
by
5.4k points