Mathematics
Grade 7
15 min
Find the missing exponent or base
Find the missing exponent or base
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Identify the base, exponent, and power in an exponential expression.
Determine a missing exponent by recognizing powers of a common base.
Solve for a missing base in equations involving perfect squares by using square roots.
Solve for a missing base in equations involving perfect cubes by using cube roots.
Apply inverse operations to find unknown bases or exponents.
Verify solutions by substituting the calculated value back into the original equation.
Ever wondered how scientists calculate population growth or how much space a 3D object takes up? 📈 Sometimes, we know the final result but need to figure out the hidden number that got us there!
In this lesson, you'll learn how to uncover those hidden numbers – either the base or the exponent – in mat...
2
Key Concepts & Vocabulary
TermDefinitionExample
BaseThe number that is multiplied by itself in an exponential expression.In $3^4$, the base is 3.
ExponentThe number that tells you how many times to multiply the base by itself.In $3^4$, the exponent is 4.
PowerThe entire expression (e.g., $3^4$) or the result of the expression (e.g., 81).$3^4$ is a power, and its value is 81.
Exponential EquationAn equation where the variable appears as an exponent or as the base of an exponential expression.$2^x = 16$ or $x^3 = 27$.
Perfect SquareA number that can be expressed as the product of an integer multiplied by itself (an integer squared).25 is a perfect square because $5^2 = 25$.
Perfect CubeA number that can be expressed as the product of an integer multiplied by itself three times (an integer cubed).64 is a perfect cube...
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Core Formulas
Rule for Finding a Missing Exponent (Same Base)
If $b^x = b^y$ and $b \neq 0, 1, -1$, then $x=y$.
To find a missing exponent, try to express both sides of the equation with the same base. Once the bases are the same, the exponents must be equal.
Rule for Finding a Missing Base (Square Root)
If $x^2 = a$ (where $a \ge 0$), then $x = \sqrt{a}$.
To find a missing base that is squared, take the square root of both sides of the equation. For Grade 7, we usually focus on the principal (positive) square root.
Rule for Finding a Missing Base (Cube Root)
If $x^3 = a$, then $x = \sqrt[3]{a}$.
To find a missing base that is cubed, take the cube root of both sides of the equation. This works for any real number 'a'.
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Challenging
If a number multiplied by itself three times is 729 (x â‹… x â‹… x = 729), what is the number?
A.243
B.9
C.27
D.81
Challenging
A large square patio is paved using 196 identical square tiles with no gaps. How many tiles are along one edge of the patio?
A.49
B.14
C.16
D.98
Challenging
The cube root of a certain number is 8. What is the number itself?
A.2
B.64
C.24
D.512
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