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Exponents and Powers - Expressing Large Numbers in Standard Form

Grade 7CBSE

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

🔑Concepts

Standard form, also known as scientific notation, is a method used to express very large numbers in a compact and readable format. Visually, a long string of digits like 150,000,000150,000,000 is condensed into a shorter expression involving a decimal and a power of 1010.

Any number in standard form is written as the product of a decimal number and a power of 1010, expressed as k×10nk \times 10^{n}. In this structure, kk is a terminating decimal such that 1k<101 \le k < 10, meaning there is exactly one non-zero digit to the left of the decimal point.

To convert a large number to standard form, we move the decimal point to the left. For every place the decimal point moves, the power of 1010 increases by 11. You can visualize the decimal point 'jumping' over digits from right to left until it rests immediately after the first non-zero digit.

The exponent nn in the power 10n10^{n} represents the total number of places the decimal point has shifted. For instance, in the number 5,0005,000, we imagine the decimal at the end (5,000.05,000.0) and move it 33 places left to get 5.05.0, resulting in n=3n = 3.

Standard form is highly effective for comparing the magnitude of very large numbers. When comparing two numbers, first look at the exponent of 1010; the number with the larger exponent is always larger. If the exponents are equal, you then compare the decimal coefficients (kk).

Powers of 1010 represent the place value system in a simplified way. For example, 101=1010^{1} = 10, 102=10010^{2} = 100, and 106=1,000,00010^{6} = 1,000,000. Visually, the exponent nn corresponds exactly to the number of zeros following the digit 11 in the expanded form of the power.

📐Formulae

Standard Form: k×10nk \times 10^{n}

Range of coefficient: 1k<101 \le k < 10

Power of ten: 10n=10×10××10n times10^{n} = \underbrace{10 \times 10 \times \dots \times 10}_{n \text{ times}}

Large number expansion: a,000,000=a×106a,000,000 = a \times 10^{6}

💡Examples

Problem 1:

Express the number 59,85,00,00059,85,00,000 in standard form.

Solution:

Step 1: Locate the decimal point. In 59,85,00,00059,85,00,000, the decimal point is at the end: 598500000.0598500000.0. \ Step 2: Move the decimal point to the left until only one digit (55) remains to the left of the decimal. \ Step 3: Count the number of places the decimal moved. Here, it moves 88 places to the left to become 5.9855.985. \ Step 4: Write the number as a product of the new decimal and 1010 raised to the power of the count. \ Final Answer: 5.985×1085.985 \times 10^{8}

Explanation:

The decimal was moved 88 places to the left to ensure the coefficient kk (which is 5.9855.985) falls between 11 and 1010.

Problem 2:

The distance between the Earth and the Sun is approximately 150,000,000150,000,000 km. Express this distance in standard form.

Solution:

Step 1: The decimal point is at the end of 150,000,000150,000,000. \ Step 2: Shift the decimal point to the left to sit between the digits 11 and 55. \ Step 3: Count the shifts: the decimal moves 88 places (1.500000001.50000000). \ Step 4: Express the result as k×10nk \times 10^{n}. \ Final Answer: 1.5×1081.5 \times 10^{8} km

Explanation:

Moving the decimal 88 places to the left results in a coefficient of 1.51.5. Since we moved 88 places, the exponent for the base 1010 is 88.