In a book store, the words of the glowsign board "MODERN BOOK STORES" are individually flashed after 5/2, 17/4 and 41/8 seconds respectively. Each word is put off after a second. What is the least time after which full name of the book store can be read?
Explanation:
The words MODERN, BOOK and STORES appear after 5/2, 17/4 and 41/8 seconds respectively and are put off after 1 second.
So, if all the words flashed together at t = 0 seconds, then
MODERN will flash after (5/2 + 1) = 7/2 seconds
BOOK will flash after (17/4 + 1) = 21/4 seconds
STORES will flash after (41/8 + 1) = 49/8 seconds.
So, all the words will flash together again after LCM(7/2, 21/4, 49/8) seconds.
∴ L.C.M. 72,214,498=L.C.M. of NumeratorsH.C.F. of Denominators=1472= 73.5 seconds
Hence, option (a).
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