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Converting mixed numbers to improper fractions

Converting Mixed Numbers to Improper Fractions. Created by Sal Khan and Monterey Institute for Technology and Education.
Video transcript
Write 5.1/4 as an improper fraction Let me remind you an improper fraction is one where the numerator is gretaer than or equal to denominator, absolute value of numerator is greater than or equal to absolute value of denominator In this situation right here we have a mixed number where 5 is the whole number and 1/4 is a proper fraction as numerator is less than denominator So write as an improper fraction I will show you the methodology So 5.1/4, the methodology is simple 5 is the same thing as 20/4 So 20/4 + 1/4 = 21/4 Another way to think is 5 x 4 = 20 + 1 = 21 So its 21/4 You take the mixed number or you take the whole part of the mixed number multiply it with the denominator & add the numerator to it. So let us see why it works. lets us see what 5.1/4 is We have 5 wholes, this is one whole let me copy it five times So that is 2, 3, 4 & that is 5 So we have 5 wholes and then we have 1/4 1/4th of a whole is like this To write it as a improper fraction Divide each of the wholes into 1/4ths This is 4, 1/4ths, another 4,1/4ths another 4,1/4ths this is another 4, 1/4ths. So how many 1/4ths we have it is 20 , 1/4ths in green That is the same thing as 5 and then we can add to that 1/4ths. Then we will get 21/4. That is the conceptual way of how it works. Multiply the whole number by the denominator and add the numertaor to it 5.1/4 = 21/4 5.1/4 =( ( 5x4) + 1)/4