Question 21 (b) - There are three bells placed at different swings in

Question 21 (b) There are three bells placed at different swings in a park, which toll at intervals of 5, 6 and 8 minutes, respectively. They all toll together when the park opens for the visitors at 10:00 a.m.. How many more times do they all toll together till the park is closed at 7:00 p.m.? Let the bells ring at 1, 2, 3 minutes At 6 minutes, all of them ring together. Now, this 6 is actually the LCM of 1, 2, 3 0 1 2 3 4 5 6 7 8 9 Where all of ring together So, Time when they ring together = LCM of 1, 2, 3 In our question , bells ring at 5, 6 and 8 minutes Thus, Time when they next ring together = LCM of 5, 6, 8 Finding LCM 5, 6, 8 2 2 5, 3, 4 5, 3, 2 2 5, 3, 1 3 5, 1, 1 5 1, 1, 1 Thus, LCM = 2 × 2 × 2 × 3 × 5 = 120 Thus, the three bells tolls together after 120 minutes, i.e. 2 hours Now, All 3 Bells first tolls at 10:00 am and tolls every 2 hours Thus, All 3 Bell tolls at 10:00 am + 2 hours = 12:00 pm All 3 Bell tolls at 12:00 pm + 2 hours = 2:00 pm All 3 Bell tolls at 2:00 pm + 2 hours = 4:00 pm All 3 Bell tolls at 4:00 pm + 2 hours = 6:00 pm And, then the park closes at 7 pm Thus, the three bells toll together 4 more times

Question 21 (b) - CBSE Class 10 Sample Paper for 2027 Boards - Maths Standard - Solutions of Sample Papers for Class 10 Boards

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