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Which of the following numbers will give 30 when rounded to the nearest ten?
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31, 10, 24, or 36.
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We have to decide which of the four numbers will round to 30 if we rounded to the nearest ten.
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Where would we place the number 31 on the number line?
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The three digit in 31 is worth three 10s, which are 30.
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So, we know that 31 comes after 30 on the number line.
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The 10 which comes after 30 is 40.
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Number 31 comes between 30 and 40 on the number line.
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35 is halfway between these two 10s.
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We could position number 31 about here on the number line.
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We know when we’re rounding a number to the nearest ten, we have to look at the ones digit.
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If the ones digit is less than five, we round down.
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The number 31 has one in the ones place.
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And we know that one is less than five, so we have to round down.
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31 rounded to the nearest ten is 30.
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So, we know that number 31 will round to 30 if we rounded to the nearest ten.
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The nearest ten to the number 10 is 10.
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The nearest ten to the number 24 is 20.
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Four is less than five, so we round down to 20.
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And the number 36 has three tens and six ones.
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So, we need to round up to the nearest ten, which is 40.
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The number which will give 30 when rounded to the nearest ten is the number 31.