Answer:
2.83
Step-by-step explanation:
25 round off is equal to 30
so we can write 2.825 = 2.83 in form of 2 digits
83 round off to 80
2.83 is equal to 2.8
The percentage of the radioactive isotope left is 25.0000%.
<h3>What is the half life?</h3>
The half life of a radioactive isotope is the time that will elapse before only half of the number of original isotopes will remain.
Now;
We are told that;
Half life (t1/2) = 55 days
Time taken (t) = 115 days
Ratio of isotope remaining = N/No
Thus;
N/No = (1/2)^t/t1/2
N/No = (1/2)^115/55
N/No = (1/2)^2
N/No =1/4
Hence, the percentage = 1/4 * 100/1 = 25.0000%
Learn more about half life of an isotope:brainly.com/question/16387602
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Answer:
Step-by-step explanation:
First change 4 3/10 to 4.3. Then you change 4.3 + -6.2 to 4.3 - 6.2.
Then you do 4.3 - 6.2 and you should get - 1.9.
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Divide total bought by 3 and multiply by 20cents:
210/3 = 70
70 x 0.20 = $14.00
Subtract the amount they paid by the amount they made:
14.00 - 6.50 = $7.50
The profit made was: $7.50