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 General Aptitude
 Problems on H.C.F and L.C.M
 Important Formulas
I.  Factors and Multiples: If a number a divides another number b exactly, we say that a is a factor of b. In this case, b is called a multiple of a.  
II.  Highest Common Factor (H.C.F.) or Greatest Common Measure (G.C.M.) or Greatest Common Divisor (G.C.D.): The H.C.F. of two or more than two numbers is the greatest number that divides each of them exactly.  


III.  Least Common Multiple (L.C.M.): The least number which is exactly divisible by each one of the given numbers is called their L.C.M.  


IV.  Product of two numbers =Product of their H.C.F. and L.C.M.  
V.  Coprimes: Two numbers are said to be coprimes if their H.C.F. is 1.  
VI.  H.C.F. and L.C.M. of Fractions:  


VII.  H.C.F. and L.C.M. of Decimal Fractions: In given numbers, make the same number of decimal places by annexing zeros in some numbers, if necessary. Considering these numbers without decimal point, find H.C.F. or L.C.M. as the case may be. Now, in the result, mark off as many decimal places as are there in each of the given numbers.  
VIII.  Comparison of Fractions: Find the L.C.M. of the denominators of the given fractions. Convert each of the fractions into an equivalent fraction with L.C.M. as the denominator, by multiplying both the numerator and denominator by the same number. The resultant fraction with the greatest numerator is the greatest.  