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The sum of 50 + 100 + 150 + 200 + …….. + 1000 is _________(a) 10000(b) 14400(c) 10500(d) 12100This question was addressed to me in class test.My doubt stems from Sum of N Terms of Arithmetic Progression topic in portion Arithmetic Progressions of Mathematics – Class 10 |
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Answer» RIGHT option is (c) 10500 Easiest explanation: Here a = 50, d = 50 and Tn = 1000. Tn = a + (n – 1)d = 1000 50 + (n – 1)50 = 1000 50 + 50n – 50 = 1000 n = 20 We know that, Sn = \(\frac {n}{2}\) (a + l) Sn = \(\frac {20}{2}\) ((50) + 1000) Sn = 10(50 + 1000) = 10500 |
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