Mathematics Grade 9 15 min

Which metric unit of length is appropriate?

Which metric unit of length is appropriate?

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1

Introduction & Learning Objectives

Learning Objectives Express metric prefixes as powers of 10. Convert between metric units of length using exponential notation. Evaluate exponential functions that model real-world growth and decay scenarios. Analyze the result of an exponential function to determine an appropriate metric unit for the answer. Justify their choice of metric unit for quantities that are extremely large or small. Interpret the scale of answers expressed in scientific notation. If a piece of paper could be folded 42 times, its thickness would reach the moon! 🌕 How would we even begin to describe that length in an understandable way? In this tutorial, we will explore how exponential functions create incredibly large or small numbers. You will learn how the metric system, with its powers-of-10 s...
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Key Concepts & Vocabulary

TermDefinitionExample Exponential FunctionA function of the form y = a * b^x, where 'a' is the initial amount, 'b' is the growth/decay factor (and b > 0, b ≠ 1), and 'x' is the number of time intervals.A bacterial culture starts with 50 cells (a=50) and doubles (b=2) every hour (x). The function is y = 50 * 2^x. Metric Prefixes as Powers of 10The metric system uses prefixes to denote multiples or fractions of a base unit (like the meter). Each prefix corresponds to a specific power of 10.The prefix 'kilo-' (as in kilometer) means 1000, or 10^3. The prefix 'milli-' (as in millimeter) means 0.001, or 10^-3. Base Unit (Length)The standard unit in the metric system for a particular quantity. For length, the base unit is the meter (m).The he...
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Core Formulas

Exponential Function Form f(x) = a \cdot b^x Used to model a quantity that changes by a constant factor over equal intervals. 'a' is the initial value (at x=0), 'b' is the growth factor (if b>1) or decay factor (if 0<b<1), and 'x' is the number of intervals. Metric Unit Conversion L_{final} = L_{initial} \times 10^{p_{initial} - p_{final}} To convert a length from an initial unit to a final unit, multiply by 10 raised to the power of the initial prefix's exponent minus the final prefix's exponent. For the base unit (meter), the prefix power 'p' is 0.

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Sample Practice Questions

Challenging
Consider the paper folding function T(n) = 0.1 ⋅ 2ⁿ mm. Around which number of folds (n) does the thickness first become a value that is best expressed in kilometers?
A.15 folds
B.24 folds
C.42 folds
D.50 folds
Challenging
A quantum wire's length is modeled by L(x) = 1 ⋅ (0.1)ˣ meters, where x is the number of energy applications. After exactly how many applications (x) is the wire's length precisely 1 nanometer?
A.3
B.6
C.9
D.10
Challenging
A bacterial colony starts at a length of 1 micrometer (μm) and doubles every hour. The length is modeled by L(t) = L₀ ⋅ 2ᵗ. What is the colony's length after 24 hours, expressed in the most appropriate unit?
A.16.8 meters (m)
B.16,777,216 micrometers (μm)
C.16.8 kilometers (km)
D.16,800 millimeters (mm)

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