Exponential Growth and Decay Practice
Use www.wolframalpha.com for any calculations if you do not have the use of a graphing
calculator at your disposal.
Each of the “a” problems were created by a student…
1.
Taylor Bellmon
13.
Karina Batista
2.
Gabriela Farfan
14.
Fernando Cordero
3.
Devonte Walker
15.
Anais Perez
4.
Ogochukwu Ononiwu
16.
Lisbeth Polanco
5.
Jose Nieves
17.
Stephanie Gutierrez
6.
Tamara Bracey
18.
Juan Cirilo
7.
Angel Alcivar
19.
Betalis Nunez
8.
Noelia Gonzalez
20.
Terrance Battle
9.
James Isabel
21.
Michael Ogundimu
10.
Yimara McMitchell, Avian Smiley
22.
rivermill.academy.org via Nicole Anorve
11.
Isaiah Clarke, Gianni Aponte
23.
Robermy Ureña
12.
Jessy Balbi
24.
Melody Rivera
1a. Rain is falling at a rate of 3% per minute. If there is 6 feet of water
in the pool, how much water will there be in 9 minutes?
(Taylor Bellmon)
1b. Rain is falling at a rate of 3% per minute. If it has been falling for
11 minutes, and there is 7 feet of water now, how much was there
originally?
2a. Gaby looked outside and saw that the snow was falling and piling
up at a rate of 2% per minute. If there are 20 inches of snow, how much
snow will there be in 40 minutes?
(Gabriela Farfan)
2b. Gaby looked outside and saw that the snow was falling and piling
up at a rate of 2% per minute. If there are 20 inches of snow now, how
much snow was there 10 minutes ago?
3a. Battery life depreciates at a rate of 10% per hour. If there is 17%
of the battery left at 2pm, how much battery life is left at 7pm? (Devonte Walker)
3b. Battery life depreciates at a rate of 10% per hour. If there is 17%
of the battery left at 2pm, how much battery life was there at 11am?
4a. Cheyenne buys a vintage lamp for $300. The lamp gains 20% of
its value each year. After 10 years, what will the value of the lamp be?
(Ogochukwu Ononiwu)
4b. Cheyenne buys a vintage lamp in 2011. In 2017 the lamp is worth
$650. If the lamp has steadily appreciated in value by 20% each year,
what was the initial value of the lamp?
5a. The tree that Jose planted was 73 inches tall. Each year, it grows
by 23%. How tall will the tree be in 5 years?
(Jose Nieves)
5b. Each year a tree grows by 23% of its height. If the tree that Jose
planted is 208 inches tall, how tall was it 5 years ago?
6a. Tamara has 10 dollars in her piggy bank. The amount increases by
5% each week. How much money will she have in a month? (Tamara Bracey)
6b. Tamara has $46 in a piggy bank at the end of the year. If the
interest rate was 5%, how much was in the piggy bank at the beginning
of the year?
7a. Angel was 50 inches tall at age 10. Each year she grows 4% taller.
How tall will she be when she is 16 years old?
(Angel Alcivar)
7b. Angel is 58 inches tall at 16 years old. If she grows at a rate of 4%
each year, how tall was she when she was 9 years old?
8a. Noelia melts at a rate of 20% every 3 minutes. In 27 minutes, how
much of Noelia is left?
(Noelia Gonzalez)
8b. Noelia has been melting at a rate of 20% every 3 minutes. If there
is 8% of Noelia remaining at this point, how much of her existed 21
minutes ago?
9a. Your bank gives you 10% interest to your account every 3 months.
If your starting amount is $42, how much money will you have in 18
months?
(James Isabel)
9b. You have $283 in your bank account. If your bank gives you 10%
interest to your account every 3 months, how much money was in your
account 15 months ago?
10a. 1% of the total number of ice cubes melts every minute. If there
are 80 ice cubes now, how many will there be in 35 minutes?
(Yimara McMitchell, Avian Smiley)
10b. There are 54 ice cubes that have been melting at a rate of 1% per
minute for one hour. How many ice cubes were there to begin with?
11a. Shane gets $6000 at the beginning of the season. The amount
increases by 8% annually. How much does Shane have after 9 years?
(Isaiah Clarke, Gianni Aponte)
11b. Shane is earning 8% annual interest on his bank account and has
$6000 in his account. How much money was in the account 5 years
ago?
12a. The population of an endangered bird is decreasing at a rate of
0.75% per year. There are currently about 200,000 of these birds.
About how many birds will there be in 100 years?
(Jessy Balbi)
12b. The bird population of an endangered species has been decreasing
for 45 years at a rate of 0.75% per year. There are currently 200,000 of
these birds. How many were there when the population began
decreasing?
13a. Daniel bought 2 houses at the beginning of the year. He’s
planning on building more houses, increasing his total by 5% each year.
How many houses will Daniel own in 10 years?
(Karina Batista)
13b. Daniel has 12 houses and has acquired new houses at a rate of 5%
per year for 12 years. How many houses did he begin with?
14a. Rico makes 30 shots in a basketball game. If he makes less shots
each game, at a 1% rate, how many shots will he make in his 5th game?
(Fernando Cordero)
14b. Rico made 41 shots in the 35th basketball game of the season. If
his shot total has increased by 1% per game, how many shots did he
make in the 1st game of the season.
15a. There are 300 car rental stores in the neighborhood. The number
of stores decreases by 3% each year. In 10 years, how many car rental
stores will there be?
(Anais Perez)
15b. There are 300 car rental stores in town. The number has been
decreasing by 3% per year. How many stores were in town 5 years ago?
16a. The population in NYC is increasing by 2% every 2 years. In 6
years, what will be NYC’s population if it is currently at 8.4 million?
(Lisbeth Polanco)
16b. If the population of NYC has increased every 2 years by 2%, and
there are 8.4 million people living there currently. How many people
lived in NYC 20 years ago?
17a. You deposit $300 into an account that earns 5% annual interest.
Find the balance after 4 years.
(Stephanie Gutierrez)
17b. You have $300 in a bank account that has been earning 5% annual
interest for 6 years. How much money was originally put into your
account?
18a. Carl buys a brand new comic book for $5 and the comic says it
appreciates by an amount of 5% each year. How much can Carl sell it
for in 25 years?
(Juan Cirilo)
18b. Carl has a comic book that is worth $4.89 and has appreciated in
value by 5% annually for 10 years. How much did Carl originally
purchase the comic book for?
19a. Water condenses at a rate of 1% per minute. If there are 12 inches
of water on the ground, how many inches will be there in 5 minutes?
(Betalis Nunez)
19b. There are 12 inches of water on the ground. If water condenses at
a rate of 1% per minute, how much water was on the ground an hour
ago?
20a. Water evaporates at a rate of 4% per hour. If 9 gallons of water are
in the sun, how much will there be in 3 days?
(Terrance Battle)
20b. There are 9 gallons of water in the sun evaporating at a rate of 4%
per hour. How many gallons were in the bucket 24 hours ago, assuming
there is consistent sunlight throughout that time period?
21a. Henry buys a car with the original value of $80,000. Over the
course of a year the car depreciates at a rate of 10%. If this continues,
what will the value of the car be in 17 years?
(Michael Ogundimu)
21b. Henry’s car is worth $22,847 in the year 2017 and has been
depreciating steadily by 10% per year since he bought the car. If the car
was purchased in 2010, how much did he pay for it initially?
22a. Each year the local country club sponsors a tennis tournament.
Play starts with 128 participants. During each round, half of the
participants are eliminated. How many players remain after 5 rounds?
(rivermill-academy.org via Nicole Anorve)
22b. There is one player left in a tennis tournament. Each round, the
number of players has decreased by 50%. How many people were in the
tournament 7 rounds ago?
23a. Michael checks flights every month and noticed that the prices
increase by 2% each month. It the price is currently $270 per person,
what is the price after 5 months?
(Robermy Ureña)
23b. Michaels flight costs $300 if the price has increased by 2% each
month, how much did the flight cost 4 months ago?
24a. Maria eats 49% of her lettuce each minute. There was originally
one pound of lettuce. How much lettuce will she have eaten after 7
minutes?
(Melody Rivera)
24b. Maria loves lettuce. She has been consuming lettuce for 3 minutes
and has a pound of lettuce left. If she eats 49% of the lettuce each
minute, how much lettuce did she begin with?