Question

An element with mass 130 grams decays by 22% per minute. How much of the element is remaining after 7 minutes, to the nearest 10th of a gram?

Answer 1

The answer to your question is 22.9 g

Explanation:

Data

mass = 130 g

rate = 22%

time = 7 min

Process

1.- Calculate the mass remaining after each minute

130 g ----------------- 100

x ----------------- 22

x = (22 x 130) / 100

x = 28.6 g

mass remaining = 130 - 28.6 = 101.4 g

101.4 g------------------ 100

x ------------------ 22

x = (22 x 101) / 100

x = 22.22

mass remaining = 101.4 - 22.22

= 79.18

79.18 g ----------------- 100

x ----------------- 22

x = (22 x 79.18)/100

x = 17.41

mass remaining = 79.18 - 17.41

= 61.76

61.76 --------------------- 100

x ---------------------- 22

x = (22 x 61.76)/100

x = 13.59

mass remaining = 61.76 . 13.59

= 48.17 g

48.17 g ----------------- 100

x ----------------- 22

x = (22 x 48.17)/100

x = 10.59

mass remaining = 48.17 - 10.59

= 37.57 g

37.57 g ----------------- 100

x ----------------- 22

x = (22 x 37.57) / 100

x = 8.26 g

mass remaining = 37.57 - 8.26

= 29.3

29.3 g ------------------- 100

x -------------------- 22

x = (22 x 29.3)/100

x = 6.45

mass remaining = 29.3 - 6.45

= 22.85 g