Grade 9 · Math · Algebra 1

9th grade Exponential growth and decay worksheet

6 printable versionsBuilding Confidence10 questions · answer keyFree · no account

Level: Building Confidence · On Level · Challenge Me

When it’s done, scan the sheet with your phone and PencilGo marks it and picks the next one. Create a free account

Version

Exponential growth and decay

Grade 9 Math Worksheet - Building Confidence

NameDate

Circle the best answer, or write your answer on the line.

Esme's class tracks duckweed on a pond. Its area grows 4% each day. Growth arrows are × (1 + rate). What number goes on each arrow of the growth table?
Jun stacks sheets of tinted film over a flashlight. Each sheet blocks 7% of the light reaching it. Decay arrows are × (1 − rate). What number goes on each arrow of the growth table?
Kira's town has 3% more people each year. Growth arrows are × (1 + rate). What number goes on each arrow of the growth table?
Every arrow: × 1.1. Milo measures an algae patch on a pond each day. The growth table shows days 0 to 2 and the arrow. What is the area, in square cm, on day 3?
Every arrow: × 0.8. Noah shines a light through sheets of tissue paper, and each sheet lets 80% of the light through. How much light, in lux, gets through 3 sheets?
Every arrow: × 0.9. Pia's science-fair filter takes out 10% of the specks on each pass. How many specks per mL are left after pass 3?
Every arrow: × 1.5. In a science video, a yeast culture grows 50% each hour. Ren copies the growth table. How many million cells are there at hour 3?
8.
Tala's science notes say y = 50(0.92)^t, where t is in hours. The factor is the number raised to the power t. What does the rule say happens each hour?
- Growth: 8% more each hour
- Decay: 8% less each hour
- Decay: 92% less each hour
9.
Zee's plant notes say y = 30(1.25)^t, where t is in weeks. The factor is the number raised to the power t. What does the rule say happens each week?
- Growth: 25% more each week
- Decay: 25% less each week
- Growth: 125% more each week
10.
Ari's filter notes say y = 800(0.6)^t, where t is the number of passes. The factor is the number raised to the power t. What does the rule say happens each pass?
- Growth: 40% more each pass
- Decay: 60% less each pass
- Decay: 40% less each pass

9th grade Exponential growth and decay worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

Exponential growth and decay. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can turn a percent rate into the factor on every arrow: 1 + r for growth, 1 − r for decay.
I can find an amount after many steps, and read the rate from a rule like y = 1200(0.85)^t.
I can find one factor for several steps and use a half-life.

Standard: F-IF.C.8b, F-LE.A.1c, A-SSE.B.3c

Words to know

exponential growth: The amount is multiplied by the same factor above 1 each step.

exponential decay: The amount is multiplied by the same factor below 1 each step.

factor (b): The number on every arrow: the new amount for each 1 you had.

percent rate (r): How much is added or taken away each step, as a percent.

half-life: The time it takes for half of a substance to be left.

Common mistakes

Your child used the percent rate itself as the multiplier, which keeps only that small part each step.

Your child used 1 plus the rate for an amount that is going down.

Your child wrote the percent as tenths instead of hundredths (5% as 0.5).

What to say

Ask: after one step, is there more or less than at the start, and by how much?

Ask: does the amount get bigger or smaller each step?

Ask: what is 5% as a decimal?

Questions parents ask

What is the most common mistake with exponential growth and decay?

Your child used the percent rate itself as the multiplier, which keeps only that small part each step.

How can I help my child with exponential growth and decay?

Ask: after one step, is there more or less than at the start, and by how much?

Are these 9th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

More algebra 1

See all Algebra 1

Every sheet you scan goes into your child’s record: dated, marked and ready for the year-end portfolio. Homeschool records