#Help Series question

15 messages · Page 1 of 1 (latest)

lofty bone
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Can someone walk me through this question and explain to me plz

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thorny fractal
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you need to find the amount made per month add them all up and divide by 12

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when r = 1 he makes £1. when r = 2 he makes £22, r = 3 he makes £52 etc

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so you need to work out the sum of 3r^3 - 2 from r = 1 to 12

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then divide by 12

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apply the standard summation of r^3 here

answer: ||£1519 || total earnings: ||£18228||

thorny fractal
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for part b

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the criminal will pay back his earnings in n weeks

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so we can set up the following equation

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sum(3r+2) from 1 to n = total earnings

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you get n = 109.076, -111.409 [both to 3dp]

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remember that n is the number of weeks for the debt to be payed so n must be 109.076

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so it will take 110 weeks for him to pay it all off

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@lofty bone

lofty bone
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👍