How many halflives have passed if 87.5% of a substance has decomposed? How many if 99.999% has decomposed?
For 87.5% decomposition 1/8 is left.
(1/8) = (1/2)^3
Three half lives is the answer
Fot 99.999% decomposition, 10^5 is left.
Solve 10^5 = (1/2)^n for the number of halflives, n. Take the log of each side of the equatiuon for a quick solution.
 👍
 👎
 👁
 ℹ️
 🚩
Answer this Question
Related Questions

maths
The halflife of lead is 22 years. How long will it take for a sample of this substance to decay to 80% of its original amount

Mathematics
In an examination conducted for 60 candidates,the number of candidate who passed in Maths is 15 more than those who passed science and 7 failed both subject 12 candidates passed both subject 1.Draw a Venn diagram to illustrate this information 2.How many

Chem
which substance cannot be decomposed by a chemical change? carbon dioxide, methane, carbon monoxide, or carbon

Maths
In an examination,60 candidates passed science or maths.if 15 passed both subjects and 9 more passed maths than science, find the number of people who passed maths and science, probability that a candidate passed exactly one subject.

math calculus
Find the halflife (in hours) of a radioactive substance that is reduced by 30 percent in 40 hours.

Math
In a group of 105 students, 70 students passed Mathematics, 60 students passed History and 45 students passed Geography; 30 students passed Mathematics and History, 35 students passed History and Geography, 25 passed Mathematics and Geography, and 15

Science
Ethan is observing chemical and physical properties of a substance. He heats a substance and observes that the substance turns from a brown solid to a black powder. He refers to several chemistry journals that claim this represents a chemical reaction.

Intergrated Science A
Which answer choices best indicate that a substance has experienced a chemical change? Select all that apply. when the substance changes temperature when the substance changes shape when the substance changes volume when a new substance is formed

C programming
Question: Write a program that reads integers from the keyboard until the user enters the sentinel value 999. The program should then print the minimum integer read, the maximum integer read and the average of all the integers. (Excluding the sentinel

Math
Alan lives 10 times as far from school as Linda. Linda lives 0.7 mile from school. Jenny lived 1/10 as far from school as Alan. Pedro lives 1/10 as far from school as jenny. How far Pedro lives from school?

Exponential Modeling
The halflife of a radioactive substance is one day, meaning that every day half of the substance has decayed. Suppose you have 100 grams of this substance. How many grams of the substance would be left after a week?

chemistry
If there are 80 milligrams of a radioactive element decays to 10 milligrams in 30 minutes then what is the elements half life in minutes? Ok i narrowed it down to either 10 or 30...but im rly confused so if u could help it wuld be grea 80 40 1 min 20 2 min

science
You are worried that a solid substance has dissolved in a beaker of water in a lab. What would be a way to separate the substance from the water? Use a magnet to draw out the solid substance from the water. Pass the solution through a filter to let the

math
In a class of 150 students 70 passed in verbal and 90 passed in aptitude.10 failed in both the subject.how many students passed in both subject

Further maths
In an examination 31 candidate passed Chemistry,29 passed Physics 3 failed both subjects.lf 50 candidates sat for the examination how many of them passed Chemistry only.

mathematics
Find the halflife (in hours) of a radioactive substance that is reduced by 30 percent in 80 hours

Calculus
Write the recurring decimal 0.abcabcabcâ€¦ as a fraction. a) (a+b+c)/999 b) (100a+10b+c)/999 c) (abc)/999 > I did this but my teacher said I was wrong d) (100c+10b+a)/999

chemistry
Which information does the boiling point give about a substance?(1 point) the types of electric charges between particles the phase of the substance the kinetic energy required to break forces between particles the temperature of the substance

science
You are worried that a solid substance has dissolved in a beaker of water in a lab. What would be a way to separate the substance from the water? Use a magnet to draw out the solid substance from the water. Pass the solution through a filter to let the

maths
In a class of 60 students,the number of students who passed biology is 6 more than the number who passed chemistry.Every student passed at least one of the two subjects and 8 students passed both subjects.How many students passed biology and chemistry.
Still need help?
You can ask a new question or browse existing questions.