The mass of cesium left afer 120 years if the original mass of cesium is 8640 with an half-life of 30 years, is 540 grams.
<h3>What is half-life?</h3>
This can be defined as the time taken for half the amount of a radioactive substance to decay.
To calculate the amount of cesium left after 120 years, we use the formua below.
Formula:
- R' = R/(
)............. Equation 1
Where:
- R = Original amount of Cesium
- R' = New amount of cesium
- T = Total time
- t = Half-life
From the question,
Given:
- R = 8640
- T = 120 years
- t = 30 years
Substitute these values into equation 1
- R' = 8640/(
) - R' = 8640/

- R' = 8640/16
- R' = 540 grams.
Hence, The mass of cesium left afer 120 years is 540 grams.
Learn more about half-life here: brainly.com/question/25750315
78 could be seventy-eight, 78 over 1, and 78/1.
21/9 + 74/9 = (21 + 74)/9 = 95/9 = 10 5/9
Answer:192
Step-by-step explanation:
Answer:
95%
Step-by-step explanation:
%Change from 800 to 40 = %Decrease
%Decrease = Old Value - New Value/Old Value × 100%
%Decrease = 800-40/800 × 100%
%Decrease = 760/800 × 100%
% Decrease = 95%(Answer)