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# Geometric sequences - c12 watch

1. a=300
r=1.05
the q asked for the total number of phones sold over 24 months
so S= (300(1.05)^24 -1) / (1.05 -1) so my answer was 13350.599 so i rounded it to 13350 but the answer in the ms is 13351 can someone explain why please????? it should round down cos it hasnt reached 13351 in the 24 month period
2. (Original post by NoorL)
a=300
r=1.05
the q asked for the total number of phones sold over 24 months
so S= (300(1.05)^24 -1) / (1.05 -1) so my answer was 13350.599 so i rounded it to 13350 but the answer in the ms is 13351 can someone explain why please????? it should round down cos it hasnt reached 13351 in the 24 month period
Hi, can you give the exact question please? That might help us work out if you misinterpreted the question
3. (Original post by Aph)
Hi, can you give the exact question please? That might help us work out if you misinterpreted the question
i am so sorry , i just noticed ur reply...
here is the question
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
4. (Original post by NoorL)
i am so sorry , i just noticed ur reply...
here is the question
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 agree with you that you can't sell half a phone so it should be 13350.
5. (Original post by Aph)
I agree with you that you can't sell half a phone so it should be 13350.
lol why does the answer not say that then :O

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