7,234,000
4.
a student used his place value chart to show a number. after the teacher instructed him to multiply his
number by 10, the chart showed 3,200.4. draw a picture of what the place value chart looked like at first.
explain how you decided what to draw on your place value chart. be sure to include your reasoning
about how the value of each digit was affected by the multiplication. use words, pictures, or numbers.

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.