Calculus 1 : Calculus

Study concepts, example questions & explanations for Calculus 1

varsity tutors app store varsity tutors android store

Example Questions

Example Question #101 : How To Find Constant Of Proportionality Of Rate

The rate of decrease of the number of baceterium due to an introduction of soap is proportional to the population. The population decreased from 15800 to 2400 between 3:00 and 5:00. Determine the expected population at 5:30.

Possible Answers:

\(\displaystyle 1809\)

\(\displaystyle 1047\)

\(\displaystyle 832\)

\(\displaystyle 1212\)

\(\displaystyle 1499\)

Correct answer:

\(\displaystyle 1499\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population decreased from 15800 to 2400 between 3:00 and 5:00, we can solve for this constant of proportionality:

\(\displaystyle 2400=15800e^{k(5-3)}\)

\(\displaystyle \frac{12}{79}=e^{2k}\)

\(\displaystyle 2k=ln(\frac{12}{79})\)

\(\displaystyle k=\frac{ln(\frac{12}{79})}{2}=-0.942\)

Now that the constant of proportionality is known, we can use it to find an expected population value relative to an initial population value due to the difference in time points. Convert minutes to decimals by dividing by 60:

\(\displaystyle P=2400e^{(-0.942)(5.5-5)} \approx 1499\)

Example Question #102 : How To Find Constant Of Proportionality Of Rate

The rate of decrease of the number of black lotuses is proportional to the population. The population decreased from 1100 to 85 between 1993 and 2013. Determine the expected population in 2015.

Possible Answers:

\(\displaystyle 42\)

\(\displaystyle 65\)

\(\displaystyle 51\)

\(\displaystyle 5\)

\(\displaystyle 13\)

Correct answer:

\(\displaystyle 51\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population decreased from 1100 to 85 between 1993 and 2013, we can solve for this constant of proportionality:

\(\displaystyle 85=1100e^{k(2013-1993)}\)

\(\displaystyle \frac{17}{220}=e^{10k}\)

\(\displaystyle 10k=ln(\frac{17}{220})\)

\(\displaystyle k=\frac{ln(\frac{17}{220})}{10}=-0.256\)

Now that the constant of proportionality is known, we can use it to find an expected population value relative to an initial population value due to the difference in time points:

\(\displaystyle P=85e^{(-0.256)(2015-2013)} \approx 51\)

Example Question #103 : Constant Of Proportionality

The rate of growth of the number of tree frogs is proportional to the population. The population increased from 43800 to 87215 between 1990 and 1995. Determine the expected population in 2015.

Possible Answers:

\(\displaystyle 2001865\)

\(\displaystyle 1377983\)

\(\displaystyle 1208617\)

\(\displaystyle 1836714\)

\(\displaystyle 987162\)

Correct answer:

\(\displaystyle 1377983\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 43800 to 87215 between 1990 and 1995, we can solve for this constant of proportionality:

\(\displaystyle 87215=43800e^{k(1995-1990)}\)

\(\displaystyle \frac{87215}{43800}=e^{5k}\)

\(\displaystyle 5k=ln(\frac{87215}{43800})\)

\(\displaystyle k=\frac{ln(\frac{87215}{43800})}{5}=0.138\)

Now that the constant of proportionality is known, we can use it to find an expected population value relative to an initial population value due to the difference in time points:

\(\displaystyle P=87215e^{(0.138)(2015-1995)} \approx 1377983\)

Example Question #104 : Constant Of Proportionality

The rate of growth of the number of glowing mushrooms in a flooded cave is proportional to the population. The population increased from 110 to 310 between January and July. Determine the expected population in October.

Possible Answers:

\(\displaystyle 521\)

\(\displaystyle 1312\)

\(\displaystyle 419\)

\(\displaystyle 677\)

\(\displaystyle 806\)

Correct answer:

\(\displaystyle 521\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 110 to 310 between January and July, we can solve for this constant of proportionality. Use the number of the months as they're ordered in the calendar:

\(\displaystyle 310=110e^{k(7-1)}\)

\(\displaystyle \frac{31}{11}=e^{6k}\)

\(\displaystyle 6k=ln(\frac{31}{11})\)

\(\displaystyle k=\frac{ln(\frac{31}{11})}{6}=0.173\)

Now that the constant of proportionality is known, we can use it to find an expected population value relative to an initial population value due to the difference in time points:

\(\displaystyle P=310e^{(0.173)(10-7)} \approx 521\)

Example Question #101 : Constant Of Proportionality

The rate of growth of the number of jackals is proportional to the population. The population increased from 1500 to 5800 between 2013 and 2015. Determine the expected population 2018.

Possible Answers:

\(\displaystyle 22573\)

\(\displaystyle 44074\)

\(\displaystyle 81922\)

\(\displaystyle 37631\)

\(\displaystyle 59078\)

Correct answer:

\(\displaystyle 44074\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 1500 to 5800 between 2013 and 2015, we can solve for this constant of proportionality:

\(\displaystyle 5800=1500e^{k(2015-2013)}\)

\(\displaystyle \frac{58}{15}=e^{2k}\)

\(\displaystyle 2k=ln(\frac{58}{15})\)

\(\displaystyle k=\frac{ln(\frac{58}{15})}{2}=0.676\)

Now that the constant of proportionality is known, we can use it to find an expected population value relative to an initial population value due to the difference in time points:

\(\displaystyle P=5800e^{(0.676)(2018-2015)} \approx 44074\)

Example Question #2792 : Functions

The rate of growth of the number of space vipers in the Milky Way is proportional to the population. The population increased from 1200  to 58000 between 2189 and 2213. Determine the expected population 2225.

Possible Answers:

\(\displaystyle 293504\)

\(\displaystyle 403285\)

\(\displaystyle 459032\)

\(\displaystyle 362778\)

\(\displaystyle 513405\)

Correct answer:

\(\displaystyle 403285\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 1200  to 58000 between 2189 and 2213, we can solve for this constant of proportionality:

\(\displaystyle 58000=1200e^{k(2213-2189)}\)

\(\displaystyle \frac{145}{3}=e^{24k}\)

\(\displaystyle 24k=ln(\frac{145}{3})\)

\(\displaystyle k=\frac{ln(\frac{145}{3})}{24}=0.1616\)

Now that the constant of proportionality is known, we can use it to find an expected population value relative to an initial population value due to the difference in time points:

\(\displaystyle P=58000e^{(0.1616)(2225-2213)} \approx 403285\)

Example Question #3827 : Calculus

The rate of growth of the number of yeast cells in rising dough is proportional to the population. The population increased from 1100 to 5300 between 3:30 and 3:15. At what point in time approximately will the population be 200,000?

Possible Answers:

\(\displaystyle 6:01\)

\(\displaystyle 5:31\)

\(\displaystyle 4:52\)

\(\displaystyle 4:05\)

\(\displaystyle 5:17\)

Correct answer:

\(\displaystyle 4:05\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 1100 to 5300 between 3:30 and 3:15, we can solve for this constant of proportionality. Treat the minutes as decimals of an hour by dividing by 60:

\(\displaystyle 5300=1100e^{k(3.5-3.25)}\)

\(\displaystyle \frac{53}{11}=e^{0.25k}\)

\(\displaystyle 0.25k=ln(\frac{53}{11})\)

\(\displaystyle k=\frac{ln(\frac{53}{11})}{0.25}=6.290\)

Now that the constant of proportionality is known, we can use it to find the specified point in time:

\(\displaystyle 200000=5300e^{6.290(t-3.5)}\)

\(\displaystyle 6.290(t-3.5)=ln(\frac{2000}{53})\)

\(\displaystyle t=3.5+\frac{ln(\frac{2000}{53})}{6.290}=4.077 \rightarrow 4:05\)

Example Question #3828 : Calculus

The rate of growth of the number of bacterial cells in a culture is proportional to the population. The population increased from 24 to 313 between 3:00 and 4:00. At what point in time apprxoimately will the population be 50,000?

Possible Answers:

\(\displaystyle 5:59\)

\(\displaystyle 6:14\)

\(\displaystyle 6:39\)

\(\displaystyle 6:52\)

\(\displaystyle 5:25\)

Correct answer:

\(\displaystyle 5:59\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 24 to 313 between 3:00 and 4:00, we can solve for this constant of proportionality:

\(\displaystyle 313=24e^{k(4-3)}\)

\(\displaystyle \frac{313}{24}=e^{k}\)

\(\displaystyle k=ln(\frac{313}{24})=2.568\)

Now that the constant of proportionality is known, we can use it to find the specified point in time:

\(\displaystyle 50000=313e^{2.568(t-4)}\)

\(\displaystyle 2.568(t-4)=ln(\frac{50000}{313})\)

\(\displaystyle t=4+\frac{ln(\frac{50000}{313})}{2.568} =5.976 \rightarrow 5:59\)

Example Question #3829 : Calculus

The rate of growth of the number of bacteriophages assaulting a culture is proportional to the population. The population increased from 11 to 165 between 1:00 and 3:00. At what point in time will the population be 800,000?

Possible Answers:

\(\displaystyle 8:41\)

\(\displaystyle 7:02\)

\(\displaystyle 8:04\)

\(\displaystyle 9:16\)

\(\displaystyle 7:33\)

Correct answer:

\(\displaystyle 9:16\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, \(\displaystyle t\)  represents a measure of elapsed time relative to this population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 11 to 165 between 1:00 and 3:00, we can solve for this constant of proportionality:

\(\displaystyle 165=11e^{k(3-1)}\)

\(\displaystyle 15=e^{2k}\)

\(\displaystyle 2k=ln(15)\)

\(\displaystyle k=\frac{ln(15)}{2}=1.354\)

Now that the constant of proportionality is known, we can use it to find the specified point in time:

\(\displaystyle 800000=165e^{1.354(t-3)}\)

\(\displaystyle 1.354(t-3)=ln(\frac{160000}{33})\)

\(\displaystyle t=3+\frac{ln(\frac{160000}{33})}{1.354}=9.268 \rightarrow 9:16\)

Example Question #2801 : Functions

The rate of growth of the number of red snapper in secluded waters is proportional to the population. The population increased from 12000 to 96000 between 2011 and 2015. What is the constant of proportionality in years-1?

Possible Answers:

\(\displaystyle 0.520\)

\(\displaystyle 0.488\)

\(\displaystyle 0.556\)

\(\displaystyle 0.693\)

\(\displaystyle 0.411\)

Correct answer:

\(\displaystyle 0.520\)

Explanation:

We're told that the rate of change of the population is proportional to the population itself, meaning that this problem deals with exponential growth/decay. The population can be modeled thusly:

\(\displaystyle p(t)=p_0e^{kt}\)

Where \(\displaystyle p_0\) is an initial population value, and \(\displaystyle k\) is the constant of proportionality.

Since the population increased from 12000 to 96000 between 2011 and 2015, we can solve for this constant of proportionality:

\(\displaystyle 96000=12000e^{k(2015-2011)}\)

\(\displaystyle 8=e^{4k}\)

\(\displaystyle 4k=ln(8)\)

\(\displaystyle k=\frac{ln(8)}{4}=0.520\)

Learning Tools by Varsity Tutors