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# geometric sequences watch

1. in the first month after opening a mobile shop sold 300 phones . a model for future sales assumes that the number of phones sold will increase by 5% per month, so that 300 * 1.05 will be sold in the second month and 300 * 1.05^2 in the third month and so on.........
A) the number of phones sold in the 24th month ... ok that was easy all i do is 300(1.05)^23

my prob is with B) the total number of phones sold in the 24th month.......... so what i am supposed to do is use the rule right; so 300(1.05^24 -1) / 1.05 - 1 ... alright so what i got as an answer was 13350.59966 so the answer should be 13350 bcz at the end of the 24 months it would not have reached 13351 yet but in the markscheme i found the answer to be 13351.......... CAN someone pleaseeeee expalin why... please asap.. btw this q is from 2014 jan C12 pp ..thanks in advance xx
2. (Original post by NoorL)
in the first month after opening a mobile shop sold 300 phones . a model for future sales assumes that the number of phones sold will increase by 5% per month, so that 300 * 1.05 will be sold in the second month and 300 * 1.05^2 in the third month and so on.........
A) the number of phones sold in the 24th month ... ok that was easy all i do is 300(1.05)^23

my prob is with B) the total number of phones sold in the 24th month.......... so what i am supposed to do is use the rule right; so 300(1.05^24 -1) / 1.05 - 1 ... alright so what i got as an answer was 13350.59966 so the answer should be 13350 bcz at the end of the 24 months it would not have reached 13351 yet but in the markscheme i found the answer to be 13351.......... CAN someone pleaseeeee expalin why... please asap.. btw this q is from 2014 jan C12 pp ..thanks in advance xx
I only learned this yesterday, forgive me if I may be wrong.

The rule is: or
3. (Original post by NoorL)
in the first month after opening a mobile shop sold 300 phones . a model for future sales assumes that the number of phones sold will increase by 5% per month, so that 300 * 1.05 will be sold in the second month and 300 * 1.05^2 in the third month and so on.........
A) the number of phones sold in the 24th month ... ok that was easy all i do is 300(1.05)^23

my prob is with B) the total number of phones sold in the 24th month.......... so what i am supposed to do is use the rule right; so 300(1.05^24 -1) / 1.05 - 1 ... alright so what i got as an answer was 13350.59966 so the answer should be 13350 bcz at the end of the 24 months it would not have reached 13351 yet but in the markscheme i found the answer to be 13351.......... CAN someone pleaseeeee expalin why... please asap.. btw this q is from 2014 jan C12 pp ..thanks in advance xx
What you're saying makes sense. The mark scheme accepts anything that rounds to 13400.
4. (Original post by notnek)
What you're saying makes sense. The mark scheme accepts anything that rounds to 13400.
u mean my answer is correct!!
5. (Original post by LelouchViRuge)
I only learned this yesterday, forgive me if I may be wrong.

The rule is: or
hahaha ya thanks xxx
6. (Original post by NoorL)
u mean my answer is correct!!
Yes. The mark scheme says awrt (anything which rounds to) 13400.
7. (Original post by notnek)
Yes. The mark scheme says awrt (anything which rounds to) 13400.
thanks a lot xxx

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