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There are 28 pupils in a class.
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The teacher has eight liters of orange juice.
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She pours 225 milliliters of orange juice for every pupil.
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How much orange juice is left over?
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The question asks us to calculate how much orange juice is left over.
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To do this, first, we need to work out how much orange juice the pupils have drunk.
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We know there are 28 pupils.
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And the teacher pours 225 milliliters of juice for each pupil.
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We need to multiply 225 by 28 to find out how much juice the pupils have drunk.
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We’re using long multiplication to find this answer.
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And we’re going to start by multiplying 225 by eight.
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Five times eight is 40.
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Two times eight is 16, plus the four we exchanged gives us 20.
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Two times eight is 16, plus the two we exchanged gives us 18.
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225 multiplied by eight is 1800.
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Next, we need to multiply 225 by 20.
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Multiplying by 20 is the same as multiplying by 10 and then by two, which is what we’re going to do.
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By writing a zero in the ones place, we’re moving the digits one place to the left into the tens column.
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Now, let’s multiply by two.
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Five times two is 10.
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Two times two is four, plus the one we exchanged gives us five.
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And our final digit, two times two is four.
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225 multiplied by 20 is 4500.
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Now we just need to add our two totals together to tell us what 225 times 28 is.
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First, we need to add in the ones column.
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Zero and zero gives us a total of zero.
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And we have the same in the tens column giving us a total of zero.
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Eight plus five is 13.
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Finally, we need to add in the thousands column.
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One and four is five, plus the one we exchanged gives us six.
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225 multiplied by 28 is 6300.
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This means that the pupils drank 6300 milliliters of orange juice.
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Now, we can work out how much juice is left over.
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To do this, we need to find the difference between eight liters and 6300 milliliters.
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Or, we need to subtract 6300 milliliters from eight liters.
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But first, we need to convert the liters into milliliters.
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One liter is equal to 1000 milliliters.
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So eight liters is equal to 8000 milliliters.
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To find the difference, we can count on from 6300 to 8000.
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If we add 700 to 6300, that will take us to 7000.
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Then, we can add 1000 to take us to 8000.
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Altogether, we added 1700.
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So the amount of orange juice leftover is 1700 milliliters, which we could also write as 1.7 liters.
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To find the answer, the first step was to calculate how much juice the pupils had drunk by multiplying 225 by 28.
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Then, we could subtract this amount from the eight liters of juice the teacher had to begin with.
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But first, we converted liters to milliliters.
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We subtracted 6300 from 8000 to give us the answer 1700 milliliters of orange juice leftover.