# Exponential function + time - math problems

#### Number of problems found: 54

• Annual growth
The population has grown from 25,000 to 33,600 in 10 years. Calculate what was the average annual population growth in%?
• RC time constant
You introduced 1 Coulomb worth of electrons into the inner volume of a dielectric material with ϵr=6. Thirty minutes later, you found that only 36.79% of the electrons were in the internal volume. Determine the conductivity σ of the dielectric material.
• Slow saving in banks
How long will it take to save € 9,000 by depositing € 200 at the beginning of each year at 2% interest?
• The half life
The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 145 grams of a radioactive isotope, how much will be left after 3 half-lives?
• Savings
The depositor regularly wants to invest the same amount of money in the financial institution at the beginning of the year and wants to save 10,000 euros at the end of the tenth year. What amount should he deposit if the annual interest rate for the annua
• Car down
Sarah buys a car costing \$12,500. It depreciates value by 8% in the first year, 10% in the second year, and 5% in the third year. Calculate the value of a car after the third year.
• Investment 2
Jack invested \$5000 in a 5-month term deposit at 4.7% p. A. . At the end of the 5-months, jack reinvested the maturity value from the first deposit into an 11-month term deposit at 7.3% p. A. What is the maturity value at the end of the second term deposi
• Precious metals
In 2006-2009, the value of precious metals changed rapidly. The data in the following table represent the total rate of return (in percentage) for platinum, gold, an silver from 2006 through 2009: Year Platinum Gold Silver 2009 62.7 25.0 56.8 2008 -41.3 4
• Microorganisms
The first generation of micro-organisms has a population of 13500 members. Each next generation is 11/10 times the previous one. Find out how many generations will reach at least three times members of the first generation.
• The crime
The crime rate of a certain city is increasing by exactly 7% each year. If there were 600 crimes in the year 1990 and the crime rate remains constant each year, determine the approximate number of crimes in the year 2025.
• Repay, interest, loan
Ramchacha takes a loan amount of 240000 from a bank for constructing a house at the rate of simple interest of 12% per annum. After 1 yr. of taking the loan he rents the house at the rate of 5200 per month. Determine the number of years he would take to r
• Compound interest
Compound interest: Clara deposited CZK 100,000 in the bank with an annual interest rate of 1.5%. Both money and interest remain deposited in the bank. How many CZK will be in the bank after 3 years?
• Combined interest
Combined interest: Carol has deposited CZK 100,000 in the bank with an annual interest rate of 1.5%. The money was put into the account 5.5.2016 and withdraw them all before Christmas 20.12.2016. How much money did she withdraw?
• Doubling
The message is spreading that each day has doubled the number of people who know about it. All know a message for 20 days. How long known it, eighth people?
• The deposit
Deposit has been placed for one year at an annual rate of 4.5%. After the added interst amount rose to € 2,612.5. Determine initial deposit.
• Population
What is the population of the city with 3% annual growth, if in 10 years the city will have 60,000 residents?
• To the cinema
Jane at 8 am got message that all 1093 school pupils will go to the cinema. Within 20 min she said it to the three friends. Each of them again for 20 minutes said to the other three. In this way the message spread further. At what time all the children in
• Car value
The car loses value 15% every year. Determine a time (in years) when its price will halve.
• The city 2
Today lives 298000 citizens in the city. How many citizens can we expect in 8 years if their annual increase is 2.4%?
• Half life
Determine the half life of bismuth, when bismuth weight from the original weight of 32 g was only 2 grams in 242 minutes.

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