Let D be a recurring decimal of the form D=0.a1a2a1a2a1a2...., where digits a1 and a2 lie between 0 and 9 . Further, at most one of them is zero. Which of the following numbers necessarily produces an integer, when multiplied by D?
A
18
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B
108
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C
198
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D
288
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Solution
The correct option is C198 D=0.a1a2a1a2....=0.a1a2×(1+0.01+0.012+....+0.01n+.....) D=0.a1a2×(1(1−0.01))=0.a1a20.99=(a1a2)99 so, integer should be k×99. ∴2×99=198