The grid model expressed as a ratio of shaded squares to total squares is _____ Written as an equivalent fraction, it is ___
Written as a decimal, it is____
Written as a percent , it is____

1  = 25/50

2 =  1/2

3 = 0.50

4 = 50%

Step-by-step explanation:

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Option D - It is the product of the initial amount and the decay factor after w weeks.

Step-by-step explanation:

Given : Ariana starts with 100 milligrams of a radioactive substance. The amount of the substance decreases by 20% each week for a number of weeks, w. The expression finds the amount of radioactive substance remaining after w weeks.

To find : Which statement about this expression is true?

Solution :

In Ariana's expression,  

100 represents the amount of substance he begins with.

and (1-0.2) i.e, 0.8 is the amount of substance left after each time period or the decay factor after w weeks.  

The given expression represents the product of initial amount and the decay factor after w weeks.

Therefore, Option D is correct.