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Decimals - Place Value in Decimals

Grade 5ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Definition of Decimals: A decimal number is a way of expressing fractions using a decimal point to separate the whole number part from the fractional part. Imagine a single whole unit (like a square) being divided into 10 or 100 equal pieces; these pieces represent the decimal parts.

The Decimal Point: This is a small dot placed between the ones place and the tenths place. It acts as a separator. For example, in the number 12.3512.35, the dot tells us that 1212 is the whole part and 0.350.35 is the part that is less than one.

Tenths Place (110\frac{1}{10}): This is the first position to the right of the decimal point. If you visualize a long rectangle divided into 1010 equal vertical bars, one bar represents 11 tenth or 0.10.1. Ten tenths make one whole.

Hundredths Place (1100\frac{1}{100}): This is the second position to the right of the decimal point. If you visualize a large square grid divided into 100100 small squares (like a 10×1010 \times 10 graph), one tiny square represents 11 hundredth or 0.010.01. It takes 1010 hundredths to make 11 tenth.

Thousandths Place (11000\frac{1}{1000}): This is the third position to the right of the decimal point. Visually, if you take one of the tiny hundredth squares and divide it further into 1010 thin strips, each strip is 11 thousandth or 0.0010.001.

Place Value Relationship: As you move from left to right in a decimal number, the value of each place becomes 1010 times smaller. Conversely, moving from right to left, each place is 1010 times larger. For example, 0.10.1 is 1010 times larger than 0.010.01.

Expanded Form: Writing a decimal as the sum of the values of its individual digits. For example, the number 5.625.62 can be visualized as 55 whole blocks, 66 tenth-strips, and 22 hundredth-squares, written as 5+610+21005 + \frac{6}{10} + \frac{2}{100}.

Equivalent Decimals: Adding zeros to the extreme right of a decimal number does not change its value. For example, 0.40.4, 0.400.40, and 0.4000.400 all represent the same amount (four tenths). Visually, 44 tenths strips occupy the same area as 4040 hundredths squares.

📐Formulae

Value of a digit=Digit×Place Value\text{Value of a digit} = \text{Digit} \times \text{Place Value}

Tenths=0.1=110\text{Tenths} = 0.1 = \frac{1}{10}

Hundredths=0.01=1100\text{Hundredths} = 0.01 = \frac{1}{100}

Thousandths=0.001=11000\text{Thousandths} = 0.001 = \frac{1}{1000}

Expanded Form (Decimal):a.bcd=a+(b×0.1)+(c×0.01)+(d×0.001)\text{Expanded Form (Decimal)}: a.bcd = a + (b \times 0.1) + (c \times 0.01) + (d \times 0.001)

Expanded Form (Fractional):a.bcd=a+b10+c100+d1000\text{Expanded Form (Fractional)}: a.bcd = a + \frac{b}{10} + \frac{c}{100} + \frac{d}{1000}

💡Examples

Problem 1:

Find the place value and the value of the underlined digit in 58.27458.2\underline{7}4.

Solution:

Step 1: Identify the position of the digit 77. It is the second digit to the right of the decimal point. Step 2: The second position to the right of the decimal point is the 'Hundredths' place. Step 3: Calculate the value: 7×1100=7100=0.077 \times \frac{1}{100} = \frac{7}{100} = 0.07.

Explanation:

We use the decimal place value chart to determine that the digits after the decimal point represent tenths, hundredths, and thousandths respectively.

Problem 2:

Write the decimal number for the following expanded form: 60+4+310+8100060 + 4 + \frac{3}{10} + \frac{8}{1000}.

Solution:

Step 1: Add the whole numbers: 60+4=6460 + 4 = 64. Step 2: Identify the tenths digit: 310=0.3\frac{3}{10} = 0.3. Step 3: Identify the hundredths digit: There is no term with 1100\frac{1}{100}, so the hundredths digit is 00. Step 4: Identify the thousandths digit: 81000=0.008\frac{8}{1000} = 0.008. Step 5: Combine them: 64+0.3+0+0.008=64.30864 + 0.3 + 0 + 0.008 = 64.308.

Explanation:

When a specific place value (like hundredths) is missing in the expanded form, we must use zero as a placeholder in the decimal number.