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Convert sixteen twentieths to a decimal.
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Well we’re gonna look at two different ways of attacking this question.
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The first way is gonna be to find an equivalent fraction with ten or a hundred or a thousand and so on as a denominator.
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And the second way is just to do the numerator divided by the denominator in a calculation.
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So let’s look at the first method first then.
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So we’re trying to find a denominator of ten or a hundred or a thousand and so on.
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Well sixteen and twenty, if I divide both of those by two, I get a denominator of ten.
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Well sixteen divided by two is eight and twenty divided by two is ten.
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Now if we think about decimals, the first decimal place is the number of tenths.
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The second decimal place is the number of hundredths.
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The third decimal place is the number of thousandths and so on.
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Now we’ve got eight-tenths.
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So that means we’ve got an eight in the tenths column.
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Now we haven’t got any whole numbers.
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So we’ve got a zero over here and we haven’t got any hundredths or any thousandths.
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So the answer is simply nought point eight.
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Now just before we move on, we could have said twenty times five is a hundred.
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So I could’ve multiplied my numerator and my denominator by five, which would’ve given me eighty hundredths.
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Now if we’d taken that approach, we’d have been left in a slightly awkward situation, because we’d be trying to put eighty in our hundredths column.
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Well because it’s just a column, it can only have one digit in it.
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So to write eighty in the hundredths column, we have to write the zero and we carry the eight over to the next biggest column.
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And we’d write that as zero carry eight.
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And we’ve got no whole numbers, so we’d have zero in this position as well.
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Now in both cases, there aren’t any digits beyond the eight.
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So all of these would be zeros.
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These trailing zeros, we don’t normally bother writing out.
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So in both cases, we have ended up with the same answer of nought point eight.
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And we could write that as we say as nought point eight zero on or nought point eight zero zero and so on.
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But we wouldn’t normally bother.
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We’d just write nought point eight.
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So let’s look at the other method then: the numerator divided by the denominator.
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Well that would be sixteen divided by twenty.
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That looks like quite a tricky calculation to do.
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But if we look carefully at the fraction, we can know that it cancels first, four is going to sixteen and four is going into twenty.
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So sixteen twentieths actually can be simplified.
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Sixteen divided by four is four and twenty divided by four is five.
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So rather than calculating sixteen divided by twenty, we could calculate four divided by five.
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So let’s write this calculation out then.
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Four, I’m gonna write four point zero zero, divided by five.
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Now let’s just copy up our decimal point here.
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And how many times do five go into four?
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Well they don’t.
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Five is bigger than four, so that goes zero times.
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So now we need to consider how many times do five go into forty, so ignoring that decimal point for now.
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Well five goes into forty eight times.
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And eight times five is forty.
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Now the difference between forty and forty is zero.
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So we’ve got our correct answer now, nought point eight.
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So just thinking about those two methods, if your denominator will easily convert a ten or a hundred or a thousand and so on, then I would suggest method one is probably the easiest.
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If it doesn’t though, then you’re gonna have to get into doing some long or short division.