CCSS.Math.Content.HSF-LE.A.1c
The standard
Recognize situations in which a quantity grows or decays by a constant percent rate per unit interval relative to another.
Common Core State Standards for Mathematics · Construct and compare linear, quadratic, and exponential models and solve problems
What this standard means
Students need to spot when a situation changes by the same percent each step, not the same amount. They should connect phrases like “increases by 8% each year” or “decreases by half each hour” to exponential growth or decay, and explain why the starting amount and multiplier matter.
Mastery means students can identify exponential situations from tables, graphs, equations, and word problems. They can tell the difference between adding 5 each time and growing by 5% each time. Common trouble spots are confusing percent change with constant difference, using the percent as the multiplier, and missing that decay uses a multiplier less than 1.
Ways to teach it
- Give pairs tables of values and have them sort them into constant difference, constant percent change, or neither, then justify each sort.
- Ask students to write two short situations, one adding $20 per week and one growing by 20% per week, then compare outcomes.
- Show three value tables and ask students to circle the exponential one and write the common multiplier.
- Use phone battery loss, population growth, or sale markdowns to model why repeated percent change creates exponential patterns.
Plan a lesson for CCSS.Math.Content.HSF-LE.A.1c
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- CCSS.Math.Content.HSF-LE.A.1b
Recognize situations in which one quantity changes at a constant rate per unit interval relative to another.