Mental arithmetic: work the following exercises in your head. do not calculate with a pencil or paper. do not use a
decimal.
think of the number seven.
now add eight to it.
now add four more.
now subtract nine.
now add three.
your answer is
14
13
12
11

Figure abcde is a regular pentagon. segment ae is located at a (2, 1) and e (4, 1). what is the perimeter of abcde? 4 units 6 units 8 units 10 units

The rate of decay of a radioactive substance depends upon the amount present initially. the mass y (mg) of the radioactive substance cobalt-60 present in a sample at time t (years) is represented by the exponential equation y=50e −0.1315 t . answer the following questions in complete sentences. 1. how does the exponential equation above compare to the equation for simple interest that is compounded continuously? explain the similarities. 2. what is the initial amount of cobalt-60 in the sample? 2. how much cobalt-60 is left after 8.4 years? show your work. 3. what would be the y-intercept of the graph? what does it represent? 4. after how many years will the amount of cobalt-60 left be 6.25 mg? explain what happens to the cobalt-60 after 50 years? 5. discuss some “real-world” examples and uses of cobalt-60

The figure below shows rectangle abcd and the triangle eca on a coordinate plane.which of the following expressions represents the perimeter of triangle of triangle eca in units