Question

todd Has a collection of 8cds and sally has a collection of 18 cds Todd is adding 9cds 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 will they have

Answer 1

Answer:

Step-by-step explanation:

Let's create some equations first.

Say M = number of months, T = Todd and S = Sally.

We know that Todd starts with 8 cds and sally starts with 18 cds.

This means when M= 0,  T = 8 and S = 18

After one month (M = 1), Todd adds 9 cds.

This means can write the following equation:

T = 8 + 9M

So after the first month (where M = 1), we can find out that Todd has

T = 8 + 9 x 1 = 8 + 9 = 17 cds

For Sally, we know she adds 7 cds per month.

S = 18 + 7M

After one month (M = 1),

S = 18 + 7 x 1 = 25 cds.

Now we are trying to find when they will have the same number of cds and how many.

This means we are trying to figure out what M = ? when Todd and Sally are equal.

So we want to find when T = S

Remember, earlier we wrote :

T = 8 + 9M

S = 18 + 7M

If T = S, this means:

8 + 9M = 18 + 7M

Gather the like terms and solve for M.

Subtract 8 from both sides.

9M = 10 + 7M

Subtract 7M from both sides

2M = 10

Divide both sides by 2

M = 5.

So in 5 months, we are saying T = S (Todd and Sally will have the same number of cds).

Put M = 5 back into our earlier equations to find out how many cds they have after 5 months.

T = 8 + 9M

T = 8 + 9 x 5

T = 53

Therefore, after 5 months Todd and Sally will have 53 cds each :)