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Message: <blockquote data-quote="imhotep" data-source="post: 27192298" data-attributes="member: 562115">1. The sequence 1 - 6 + 2 -7 + 3 - 8 + 4 - 9 ........  (100 terms)Can be considered as two sequences (1 + 2 + 3 +................)  (50 terms)   and  -( 6+ 7 + 8 + 9 +.......) (50 terms)Just do the additions for both separately and subtract.However,,,, the easy method. Just consider the whole sequence as pairs. Group two adjacent numbers.(1 - 6) + (2 -7) + (3 -8) + (4 -9) +........Each pair within the brackets adds up to  -5.Hence the answer is -5 x 50 = -250. (because there are 50 pairs) - So you need to select B.2. Geometric progressions are ln the form of   a, ar, ar^2, ar^3, ar^4, ...........So ar^2 = 0.5 and ar^4 = 0.03125.Divide one by the other gives r^2 = 0.03125/0.5 and r= SQR(0.03125/0.5) = 0.25So the answer is (ii) & (iii)  Both forms are correct.3. Answer C4. Answer C</blockquote>

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