The sign of the result depends on whether the exponent is odd or even: - If the exponent is odd, the result is negative. - If the exponent is even, the result is positive.
"Exponent" refers to the number that indicates how many times to multiply the base. "Power" refers to the result of raising the base to the exponent. For example, in 2^3, 3 is the exponent, and 8 is the power.
CBSE Notes Class 7 Chapter 11 Exponents and Powers
Chapter 11 of CBSE Class 7 Mathematics, "Exponents and Powers," introduces students to the concise representation of large numbers using exponents. It explores concepts such as base and exponent, simplifying expressions using laws of exponents, and representing numbers in standard form. This chapter helps students understand operations involving powers, including multiplication and division, and using negative exponents. It lays a strong foundation for handling larger numerical values efficiently in further mathematical studies and practical applications.
1.0Exponent Form of a Number
Exponent form is used to express large numbers in a compact and readable way. For example, the mass of an electron is 9.1×10−31 kg, and the world population is around 7×109. In exponent notation, if x is a rational number, xn represents the product of x multiplied by itself n times, where x is the base and n is the exponent.
For example, 7×7×7×7=74. If the base is negative, the rule remains the same, but the sign depends on whether the exponent is odd (negative value) or even (positive value).
Exponents are shorthand for repeated multiplication, and expressions like a3b2 (read as "a cubed b squared") represent repeated factors. Additionally, the order of multiplication does not affect the result, so a5b3 is the same as b3a5.
2.0Laws of Exponents
Product of Powers Rule: am×an=am+n
Power of a Power Rule: (am)n=amn
Power of a Product Rule: (ab)n=an×bn
Zero Exponent Rule: a0=1
Negative Exponent Rule: a−n=an1
Quotient Law of Exponent: anam=am−n
These rules help simplify and solve expressions involving exponents.
Example 7: Find the value of the following using laws of exponents.
8×(−2)5×2728×34
Solution:
23×(−1)5(2)5×3328×34=(−1)28−3−5×34−3
−1×20×3=−1×3=−3(20=1)
6.0Sample Questions on Exponents and Powers
What is an exponent?
Ans: An exponent is the number that indicates how many times the base number is multiplied by itself. For example, in 23, 2 is the base, and 3 is the exponent, meaning 2×2×2=8.
What is the meaning of negative exponents?
Ans: A negative exponent indicates the reciprocal of the base raised to the opposite positive exponent. For example, 2−3=231=81.
What is the rule for multiplying powers with the same base?
Ans: When multiplying powers with the same base, add the exponents:
am×an=am+n
What is the rule for dividing powers with the same base?
Ans: When dividing powers with the same base, subtract the exponents:
anam=am−n
What happens when the exponent is 0?
Ans: Any non-zero number raised to the power of 0 is 1: a0=1(fora=0)
What is scientific notation?
Ans: Scientific notation is a way of expressing very large or small numbers in the form k×10n, where 1≤k<10 and n is an integer. For example, 3.0×108 represents 300,000,000.
How do you express numbers with fractional exponents?
Ans: A fractional exponent represents both a root and a power. For example, anm=nam, which means the nth root of a raised to the power m.
What is the difference between powers and exponents?
Ans: "Exponent" refers to the number that indicates how many times to multiply the base. "Power" refers to the result of raising the base to the exponent. For example, in 23, 3 is the exponent, and 8 is the power.
7.0Key Features of Class 7 Chapter 11 : Exponents and Powers
Introduction to Exponents: Simple explanation of powers, bases, and exponents with everyday examples.
Laws of Exponents: Clear and detailed coverage of the important laws, like multiplication, division, and power of a power.
Negative Exponents: Easy-to-understand rules for dealing with negative powers.
Standard Form: Explanation of expressing large and small numbers in standard form using exponents.
Use of Exponents in Real Life: Practical applications of exponents in scientific and mathematical contexts.
Solved Examples: Step-by-step examples to demonstrate the correct use of exponent rules.
Practice Problems: Varied exercises to develop problem-solving skills and strengthen conceptual clarity.