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?
Correct answer:

Tips for related online calculators
Do you want to convert time units like minutes to seconds?
You need to know the following knowledge to solve this word math problem:
Units of physical quantities:
Grade of the word problem:
Related math problems and questions:
- Radioactivity
After 548 hours decreases the activity of a radioactive substance to 1/9 of the initial value. What is the half-life of the substance?
- Radioactive material
A radioactive material loses 10% of its mass each year. What proportion will be left there after n=6 years?
- 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.
- Suppose 2
Suppose that the half-life of a substance is 250 years. If there were initially 100 g of the substance, a. Give an exponential model for the situation b. How much will remain after 500 years?
- Virus
We have a virus that lives one hour. Every half hour produce two child viruses. What will be the living population of the virus after 3.5 hours?
- Loan pay back
Imagine a situation a student got access to a student loan of about 1000000 naira to pay all his fees throughout his undergraduate studies without having an extra year. He is expected to pay back the money 5 year after securing a job and it took him 2 1/3
- Suppose 6
Suppose the life span of a revolutionary light bulb is normally distributed with a mean life span of 70 thousand hours and a standard deviation of 3 thousand hours. If a light bulb is chosen at random: a) what is the probability the life span will be with
- Acid solution
By adding 250 grams of a 96% sulfuric acid solution to its 3% solution, we changed its initial concentration to 25%. How many grams of 3% of the acid was used for dilution?
- Discount sale
After the discount, the computer costs 9600, - CZK. How much did it cost when the price was reduced: a) by half b) by a third c) by one fifth and then by 160 CZK
- Heating plant
Workers dump imported coke at the heating plant. On the first day used half of the amount, the second day three quarters the rest and on the third day left 120 tons. How much coke did they dump at the heating plant?
- Oak forest
It takes 45 years to grow from Little oak Oak. How long will it take for an oak forest to grow out of 286 Little oaks?
- A koala
A koala lives to be 14 years old in the wild. How much longer will a 2-year-old koala probably live?
- Depreciated 37171
The initial price of the machine is 23,000 euros. Every year, 12% of its cost is depreciated due to wear and tear. What value will the machine have after six years?
- Depreciated 37521
The initial price of the machine is 12000 euros. 21% of its price is depreciated every year due to wear and tear. What value will the machine have after five years?
- A burger
The water starts with 41 1/4 cups of water how much water is left after ten 3 5/8 Scoops of water are removed?
- Concentration
How many grams of 65% and 50% acid is to be mixed to give 240 g acid with a concentration of 60%?
- The ship
The ship went upstream speed of 20 km/h in relation to water. River flows at speed 10 km/h. After half an hour, he stopped and returned downstream to the starting point. How long it took way back when even if downstream speed of ship is 20 km/h in relatio