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Math(arithmetic sequence)

發問:

1.Find the smallest multiple and the largest multiple of 9 between 300 and 800.(b)Find the sum of all multiples of 9 lying between 300 and 800.2.(a)Find the sum of all multiples of 3 lying between 400 and 500.(b)Find the sum of all multiples of 6 lying between 400 and 500.(c)Between 400 and 500,Find the sum of... 顯示更多 1.Find the smallest multiple and the largest multiple of 9 between 300 and 800. (b)Find the sum of all multiples of 9 lying between 300 and 800. 2.(a)Find the sum of all multiples of 3 lying between 400 and 500. (b)Find the sum of all multiples of 6 lying between 400 and 500. (c)Between 400 and 500,Find the sum of all integers that are multiples of 3 but not multiples of 6.

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1.Find the smallest multiple and the largest multiple of 9 between 300 and 800. smallest multiple = 306 largest multiple = 792 (b)Find the sum of all multiples of 9 lying between 300 and 800. T(n) = 306 + 9(n - 1) 306 + 9(n - 1) = 792 n = 55 S(55) = (55/2)(306 + 792) = 30195 ---------------------------------------------------- 2.(a)Find the sum of all multiples of 3 lying between 400 and 500. smallest multiple = 402 largest multiple = 498 T(n) = 402 + 3(n - 1) 402 + 3(n - 1) = 498 n = 33 S(33) = (33/2)(402 + 498) = 14850 (b)Find the sum of all multiples of 6 lying between 400 and 500. smallest multiple = 402 largest multiple = 498 T(n) = 402 + 6(n - 1) 402 + 6(n - 1) = 498 n = 17 S(17) = (17/2)(402 + 498) = 7650 (c)Between 400 and 500,Find the sum of all integers that are multiples of 3 but not multiples of 6. 14850 - 7650 = 7200 2007-10-12 19:12:45 補充： oh! my god, 慢左用左好多心機做, 請投我一票啦, 唔該

其他解答:

下, 佢個答案好清楚咩? 步驟差不多, 只係多咗句 [oh! my god, 慢左 用左好多心機做, 請投我一票啦, 唔該] 嘩, 咁樣都幾造馬!|||||1. a = 9 d = 9 smallest >300 9+(n-1)*9 > 300 n > 33.33.. Take n = 34 T(34) = 9 + (34-1 )*9 = 306 largest 400 n > 133.33 Take n = 134 T(134) = 3+(134-1)*3 = 402 3+(k-1)*3