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# Sequences problem watch

1. Hey guys,

An investor puts £4000 in an account. Every month thereafter she deposits another £200. How much money in total will she have invested at the start of a) the 10th month and b) the mth month (Note at the start of the 6th month she will have made only 5 deposits of £200)

I'm really confused on the bold bit, because surely she would have 6 deposits on the 6th month? The first month starts from when she gained £4200, right?

With that being said, for A) I would have thought it would be 4000 + 10 x 200? But this is incorrect, why? :/

and I'm not too sure on the mth month, eek.
2. (Original post by rm_27)
Hey guys,

An investor puts £4000 in an account. Every month thereafter she deposits another £200. How much money in total will she have invested at the start of a) the 10th month and b) the mth month (Note at the start of the 6th month she will have made only 5 deposits of £200)

I'm really confused on the bold bit, because surely she would have 6 deposits on the 6th month? The first month starts from when she gained £4200, right?

With that being said, for A) I would have thought it would be 4000 + 10 x 200? But this is incorrect, why? :/

and I'm not too sure on the mth month, eek.
1st month : £4000
2nd month : £(4000 +1 x 200)
2nd month : £(4000 +2 x 200)
3rd month : £(4000 +3 x 200)

10th month : £(4000 +? x 200)

mth month : £(4000 +? x 200)
3. (Original post by rm_27)
Hey guys,

An investor puts £4000 in an account. Every month thereafter she deposits another £200. How much money in total will she have invested at the start of a) the 10th month and b) the mth month (Note at the start of the 6th month she will have made only 5 deposits of £200)

I'm really confused on the bold bit, because surely she would have 6 deposits on the 6th month? The first month starts from when she gained £4200, right?

With that being said, for A) I would have thought it would be 4000 + 10 x 200? But this is incorrect, why? :/

and I'm not too sure on the mth month, eek.
It says every month thereafter meaning that the investments go like this:
month, investment, total account
1, 4000, 4000
2, 200, 4200
3, 200, 4400,
...
10, 200, ____ (you work this number out!)
4. a) The equation for it would be: Un=a+(n-1)d

10th month= 4000+(10-1)200 ---> 10th month= 4000+(9)200 ---> 10th month= 4000+1800 -----> 10th month= 5800

I think this is correct, but someone please correct me if I'm wrong.
5. (Original post by asian.mikehunt)
a) The equation for it would be: Un=a+(n-1)d

10th month= 4000+(10-1)200 ---> 10th month= 4000+(9)200 ---> 10th month= 4000+1800 -----> 10th month= 5800

I think this is correct, but someone please correct me if I'm wrong.
6. (Original post by Asian.Guy)
What did I do wrong?
Is this the same person because the username is slightly different.
7. Yes, sorry. I wanted to change my username so I just made a new account. Edited the comment so no-one would notice :P

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