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
2/5 of the job remains to be done.
Answer:
Add the two angles. The two number correspond to a part of the larger LMN angle, I think, so they should equal the total when combined, I think.
the ratio of the number of kids is 4:7
that means for every 7 kids we have 4 adults
7 kids ---- 4 adults
the difference is 3
we dived the difference of the kids between the difference of the ratio
150/3 = 50
the number we obtained must be multiply by the ratio of each part
7(50) = 350 number of kids
4(50)=200 number of adults
there are 200 adults at the fun fair