WEBVTT
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One day, a flock of birds flew for two and three-quarter hours.
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The next day, they flew for three and four-fifths hours.
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How many hours did the birds fly for in total?
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To find the total number of hours that the birds flew for, we need to add together two and three-quarter hours and three and four-fifths hours.
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At the moment, these fractions both have different denominators.
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We have an amount of quarters and an amount of fifths.
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Before we can add these two numbers together, we need to make sure that the denominators are the same.
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We need to find a number which we can divide by four and by five.
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20 can be divided by four and five.
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To get from four to 20, we need to multiply by five.
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We need to do the same to the number on top, the numerator.
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What is three multiplied by five?
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15.
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We don’t need to do anything to the whole number, number two.
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Two and three-quarters is equal to two and fifteen twentieths.
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Similarly, we don’t need to do anything to the three, the whole number.
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We can just add the whole numbers together, two and three.
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To get from five to 20, we had to multiply by four.
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And so, we need to do the same to the numerator.
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Four multiplied by four gives us sixteen twentieths.
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Oh, now we can add our two numbers together because the denominators in our fractions are the same.
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First, we can add the whole numbers.
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Two plus three equals five.
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And now, we need to add the twentieths.
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We have fifteen twentieths and sixteen twentieths.
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How many twentieths do we have altogether?
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16 plus 15 equals 31.
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Thirty-one twentieths is an improper fraction.
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It’s top heavy; the number on the top, the numerator, is heavier or larger than the number on the bottom.
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31 is more than 20.
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This means, our fraction is worth more than one.
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So, we can exchange twenty twentieths for one whole, which means now we have six.
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And because we exchanged 20 of our twentieths, we no longer have thirty-one twentieths.
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We have 11.
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31 subtract 20 is 11.
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If a flock of birds flew for two and three-quarter hours on one day and on the next day flew for three and four-fifths hours, the total number of hours the birds flew is six and eleven twentieths hours.
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We added together our two fractions.
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Because the denominators were different, we had to change the fractions to make the denominators the same.
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Then, we were able to add the two fractions together, which gave us a total of five and thirty-one twentieths.
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But this is an improper fraction.
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So, we simplified it to six and eleven twentieths.
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The total number of hours the birds flew is six and eleven twentieths hours.