Grade 9 · Math · Algebra 1

9th grade Exponential growth and decay worksheet

6 printable versionsOn Level10 questions · answer keyFree · no account

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

NameDate

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

Each squeeze takes 30% of the water left in Luz's sponge. What number goes on each arrow of the growth table?
Milo's town has 4,500 people and grows 3% each year. To the nearest whole number, how many people live there after 5 years?
Noah looks up a used bike worth $360. Its value drops 15% each year. To the nearest dollar, what is it worth after 4 years?
Pia shines 800 lux of light through 3 sheets of thick paper. Each sheet blocks 30% of the light reaching it. To the nearest whole lux, how much gets through?
Tala's water has 2000 specks per mL. A filter takes out 40% of the specks on each pass. How many specks per mL are left after 3 passes?
A used scooter's value is y = 240(0.97)^t after t months. Bo asks: by what percent does it drop each month?
7.
Jun's town has 6,000 people and shrinks 4% each year. Which equation gives the amount y after t years?
- y = 6000 − 240t
- y = 6000(0.96)^t
- y = 6000(1.04)^t
- y = 6000(0.04)^t
8.
A fern patch in Kira's garden bed covers 20 square cm and grows 15% each week. Which equation gives the amount y after t weeks?
- y = 20 + 3t
- y = 20(1.15)^t
- y = 20(0.15)^t
9.
Luz shines 900 lux through layers of film, and each layer blocks 25% of the light reaching it. Which equation gives the amount y after t layers?
- y = 900(1.25)^t
- y = 900(0.75)^t
- y = 900(0.25)^t
10.
Milo's bike club has 50 members and grows 8% each month. Which equation gives the amount y after t months?
- y = 50(0.08)^t
- y = 50 + 4t
- y = 50(1.08)^t

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

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

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.

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).

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?

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.

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