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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 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog

Out of 50 students surveyed, 16 have a dog. based on these results, predict how many of the 280 students in the school have a dog.