Question

Virginia starts with 200 milligrams of a radioactive substance. The amount of the substance decreases by 25% each week for a number of weeks, w. The expression 200(1−0.25)w finds the amount of radioactive substance remaining after w weeks. Which statement about this expression is true?

A: It is the product of the initial amount and the decay factor after w weeks.




B: It is the difference between the initial amount and the percent decrease.




C: It is the difference between the initial amount and the decay factor after w weeks.




D: It is the initial amount raised to the decay factor after w weeks.

Answer 1

It is the product of the initial amount and the decay factor after weeks.

Explanation:

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Answer 2

Answer: option 'A' is correct.

Explanation:

Since we have given that

Quantity of radioactive substance = 200 milligrams

Rate of decay = 25%

Number of weeks = w

As we know the formula for "Compound Interest ":

`A=P(1-(r)/(100))^w\\\\A=200(1-0.25)^w`

So, here , P=200 milligrams i.e. the initial amount

So, It is the product of the initial amount and the decay factor after w weeks.

Hence, option 'A' is correct.