# Video: Writing Decimals Using Part–Whole Models

The large square represents one whole. Write a decimal that represents the shaded area.

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### Video Transcript

The large square represents one whole. Write a decimal that represents the shaded area.

In this question, we’re given a large square. This large square measures 10 squares by 10 squares, which means it’s been divided into 100 smaller squares or 100 equal parts. So we know each of the smaller squares represents one hundredth. So to help us find the decimal that represents the shaded area, we need to know how many of these smaller squares have been shaded. We need to know how many hundredths are shaded. There are 10 squares in each column, so let’s count in tens. 10, 20, 30, 40, 50. And one more shaded square makes 51. 51 out of 100 squares are shaded.

We’ve written the shaded area as a fraction. How would we write it as a decimal? We know the large square represents one whole, and fifty-one hundredths have been shaded, so we know our number is less than one. In other words, it has zero ones. And we know the fractional part of our number is fifty-one hundredths, so we can write our five digit and our one digit to represent fifty-one hundredths. The decimal which represents the shaded area is fifty-one hundredths, which we write as 0.51.