Element X is a radioactive isotope such that every 61 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 20 grams, how long would it be until the mass of the sample reached 16 grams, to the nearest tenth of a year?

19.6

Step-by-step explanation:

when rotating a figure 180 degrees, imagine that you are able to take the figure and turn it clockwise or counterclockwise around a center point. to rotate a figure 180 degrees, you will need to apply the rule (x, y) → (-x, -y). start by using a coordinate grid with coordinates for each vertex of the figure. the center point of the coordinate grid is located at (0, 0), which is what you will rotate the figure around. write down the original coordinates of the shape you are going to rotate. then, apply the rule. for example, coordinate (1, 2) becomes (-1, -2). another example would be, coordinate (-4, -2) becoming (4, 2). after you change each original coordinate to the rotated coordinate, you will draw your new figure.

step-by-step explanation:

question

given the diagram below, what is md?

the sum of the interior angles is 360°

take away from 360 the sum of the knows angles and you will have the angle d.

360 - 108 - 108 - 72 = 72°