Anupam279 Posted February 20, 2003 Share Posted February 20, 2003 I know how to calculate LCM & HCF. I am looking for Questions that do not expliclity say find the LCM or HCF, but require the use of this concept to solve the question. Usually such Question are word problems. Can anyone help with examples and also tell the answers so that I can verify my understanding of the concept. Thanks Quote Link to comment Share on other sites More sharing options...
pankajagg Posted February 21, 2003 Share Posted February 21, 2003 anupam try this one There are 2 persons A & B running in a cricle, A completes one revolution in 4 min and B completes one revolution in 7 min. They start running togather, after how much time A & B will meet at starting point. (Assume any missing information) a) They move in opposite directions b) They move in same direction. Quote Link to comment Share on other sites More sharing options...
Anupam279 Posted February 25, 2003 Author Share Posted February 25, 2003 I tried the same direction problem, with the answer being 28 minutes, but I am not clear as to how will the answer and why will it be different if they were moving in opp direction? Pnakaj or anybody else? Originally posted by pankajagg anupam try this one There are 2 persons A & B running in a cricle, A completes one revolution in 4 min and B completes one revolution in 7 min. They start running togather, after how much time A & B will meet at starting point. (Assume any missing information) a) They move in opposite directions b) They move in same direction. Quote Link to comment Share on other sites More sharing options...
pankajagg Posted February 27, 2003 Share Posted February 27, 2003 Answer will not be different, even if they are moving in opp direction A completes one round in 4 min and this is irrespective of B's revolution B completes its revolution in 7 min in any direction so the answer will be the same Had the question been when will they first meet then directions would have matter Quote Link to comment Share on other sites More sharing options...
phxmba Posted March 17, 2003 Share Posted March 17, 2003 I found another LCM application problem The front wheels of a toy truck are 4 inches in circumference. The back wheels are 7 inches in circumference. If the truck travels in a straight line without slippage, how many inches will the truck have traveled when the front wheels have made 12 more revolutions than the back wheels? (A) 112 (B) 64 © 48 (D) 36 (E) 28 Quote Link to comment Share on other sites More sharing options...
anuradha Posted March 18, 2003 Share Posted March 18, 2003 Ans is 112. Answer should be multiples of 4 and 7. so it is 28, 56, 112.....and so on suppose if we choose 28, 56, and 112 then 4 will take (28/4) 7 revolution and 7 will take (7/28) 4 revolutions and the difference is (4-7) 3....but we are looking for difference of 12. 4 will take (56/4) 14 revolution and 7 will take (56/7) 8 so the difference is (14-7) 7...which doesnt clik 4 will take (112/4) 28 and 7 will take (112/7) 16 and difference is 12 which is the correct. Quote Link to comment Share on other sites More sharing options...
phxmba Posted March 18, 2003 Share Posted March 18, 2003 Option (A) 112 is correct Quote Link to comment Share on other sites More sharing options...
peterabraham Posted June 29, 2010 Share Posted June 29, 2010 Method1: HCF = 28 => 4X28=112 Method2: D=7n=4(n+12) 7n=4n+48 3n=48 n=16 D=7x16=4(16+12)=112 inches Quote Link to comment Share on other sites More sharing options...
Registerviplav Posted July 7, 2010 Share Posted July 7, 2010 @peterabraham: The one you are quoting should be LCM LCM is 28. HCF is 1 because 4 and 7 are relatively prime to each other. Quote Link to comment Share on other sites More sharing options...
peterabraham Posted August 25, 2010 Share Posted August 25, 2010 Oops. It is L.C.M. Thanks. Method1: HCF = 28 => 4X28=112 Method2: D=7n=4(n+12) 7n=4n+48 3n=48 n=16 D=7x16=4(16+12)=112 inches Quote Link to comment Share on other sites More sharing options...
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