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help to solve this addmath's question
TSharuko_08051
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Jan 13 2018, 09:46 PM, updated 7y ago
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New Member
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An arithmetic progression has 10 terms. The first term is 6 and the sum of all the odd terms is 250. Find the common difference. (come from form 5 chapter 1 progression) help me formula 1.Tn=a+(n-1)d 2.Sn=n/2(2a+(n-1)d) 3.Sn=n/2(a+Tn) a→FIRST TERM d→COMMON DIFFERENCE the correct answer is 11 but I find the answer is 22......😢 This post has been edited by haruko_08051: Jan 13 2018, 10:48 PM
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CKKwan
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Jan 13 2018, 09:51 PM
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Just assume that it has 5 terms.
If I remember correctly the formula is 250 = 5/2 (6 + b), where b should be resolved to 94. Common difference for the odd terms are (94 - 6) / 4 = 22
So if there are 10 terms, the common difference should be 11?
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TSharuko_08051
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Jan 13 2018, 10:53 PM
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New Member
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QUOTE(CKKwan @ Jan 13 2018, 10:51 PM) Just assume that it has 5 terms. If I remember correctly the formula is 250 = 5/2 (6 + b), where b should be resolved to 94. Common difference for the odd terms are (94 - 6) / 4 = 22 So if there are 10 terms, the common difference should be 11? how I can get the answer?? divide by 2? I want know the reason.....
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CKKwan
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Jan 14 2018, 08:21 AM
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QUOTE(haruko_08051 @ Jan 13 2018, 10:53 PM) how I can get the answer?? divide by 2? I want know the reason..... Answer is already mentioned clearly in my earlier post. Ain't gonna help you to do your homework. BTW, the formula that you have added earlier is correct, but you have chosen the wrong formula for this question.
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