Video: GCSE Mathematics Foundation Tier Pack 4 • Paper 1 • Question 2

GCSE Mathematics Foundation Tier Pack 4 • Paper 1 • Question 2

02:23

Video Transcript

Convert eleven twenty-fifths to a decimal.

This is a tricky one. Usually, we can convert a fraction with a denominator of 10, 100, or 1000 into a decimal really easily since there are columns after the decimal point for tenths, one hundredths, and the thousandths. An alternative way to think about it is to remember that the fraction line means divide.

And we can easily divide by 10, 100, and 1000 by moving the digits to the right one, two, or three spaces, respectively. The denominator of our fraction is not one of these numbers. If possible then, we need to make it into one.

25 is a factor of 100. In fact, 25 is multiplied by four is 100. We can check that because multiplying by four is the same as doubling, which is timesing by two, and doubling again. 25 multiplied by two is 50. And when we multiply it by two again, we get 100. So we can multiply the denominator of this fraction by four to get 100.

Since we want to create an equivalent fraction — that’s a fraction that has the same value — we’re also going to need to do the same to the numerator. 11 multiplied by four is 44. So eleven twenty-fifths is equivalent of forty-four one hundredths. Remember we said that the fraction line means to divide. So actually, we’re working out 44 divided by 100. And to divide by 100, we said we move the digits to the right two spaces. 44 divided by 100 is 0.44. So forty-four one hundredths is the same as 0.44.

In fact, a good way to remember this is to remember that when the denominator is 10, there will be one digit after the decimal point. When it’s 100, there will be two digits after the decimal point. And when it’s 1000, there will be three digits after the decimal point.

The number of digits after the decimal point is equal to the number of zeros. 100 has two zeros. So in this one, there’ll be two digits after the decimal point.

Once again, forty-four one hundredths is equal to 0.44. So eleven twenty-fifths as a decimal is 0.44.

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