a2zinterviews

21.	A, B and C start at the same time in the same direction to run around a circular stadium. A complete a round in 252 seconds, 308 seconds and C in 198 seconds, all starting at the same point. After what time will they meet again at the starting point?
	A.  45 minutes
	B.  26 minutes and 18 seconds
	C.  42 minutes and 36 seconds
	D.  46 minutes and 12 seconds

Solution

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.

22.	The least number which when divided by 12, 15, 20 and 54 leaves in each case a remainder of 8, is
	A.  544
	B.  536
	C.  548
	D.  722

Solution

Required number = (L.C.M. of 12, 15, 20, 54) ‹=› 540 + 8 = 548.

23.	The L.C.M. of 3, 2.7 and 0.09 is
	A.  2.7
	B.  0.27
	C.  0.027
	D.  27

Solution

Given numbers are 3.00, 2.70 and 0.09. L.C.M. of 300, 270 and 9 is 2700. L.C.M. of given mumbers = 27.00 = 27.

24.	The H.C.F of two numbers is 11 and their L.C.M. is 693. If one of the numbers is 77. Find the other.
	A.  69
	B.  99
	C.  119
	D.  129

Solution

Other number = [11 x 693 / 77] = 99

25.	The greatest number that exactly divides 105, 1001 and 2436 is
	A.  3
	B.  7
	C.  11
	D.  21

Solution

H.C.F of 2436 and 1001 is 7. Also H.C.F. of 105 and 7 is 7. Therefore H.C.F. of 105, 1001 and 2436 is 7.