Exercise :: Problems on H.C.F and L.C.M  General Questions
 Problems on H.C.F and L.C.M  Important Formulas
 Problems on H.C.F and L.C.M  General Questions
11.  Find the lowest common multiple of 24, 36 and 40. 

Answer: Option C Explanation: 2  24  36  40  2  12  18  20  2  6  9  10  3  3  9  5   1  3  5 L.C.M. = 2 x 2 x 2 x 3 x 3 x 5 = 360. 
12.  The least number which should be added to 2497 so that the sum is exactly divisible by 5, 6, 4 and 3 is: 

Answer: Option C Explanation: L.C.M. of 5, 6, 4 and 3 = 60. On dividing 2497 by 60, the remainder is 37. Number to be added = (60  37) = 23. 
13. 


Answer: Option C Explanation: 128352) 238368 ( 1 128352  110016 ) 128352 ( 1 110016  18336 ) 110016 ( 6 110016  x  So, H.C.F. of 128352 and 238368 = 18336. 128352 128352 ÷ 18336 7 Therefore,  =  =  238368 238368 ÷ 18336 13 
14.  The least number which when divided by 5, 6 , 7 and 8 leaves a remainder 3, but when divided by 9 leaves no remainder, is: 

Answer: Option B Explanation: L.C.M. of 5, 6, 7, 8 = 840. Required number is of the form 840k + 3 Least value of k for which (840k + 3) is divisible by 9 is k = 2. Required number = (840 x 2 + 3) = 1683. 
15.  A, B and C start at the same time in the same direction to run around a circular stadium. A completes a round in 252 seconds, B in 308 seconds and c in 198 seconds, all starting at the same point. After what time will they again at the starting point ? 

Answer: Option D Explanation: L.C.M. of 252, 308 and 198 = 2772. So, A, B and C will again meet at the starting point in 2772 sec. i.e., 46 min. 12 sec. 