2 answers:
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Answer:
120 grams will be left after 180 years.
Step-by-step explanation:
A radioactive half-life refers to the amount of time it takes for half of the original isotope to decay and its given by
where,
= quantity of the substance remaining
= initial quantity of the substance
= time elapsed
= half life of the substance
From the information given we know that:
- The initial quantity is 480 g,
- The half-life is 90 years,
- 180 years is the time elapsed.
And we want to find how much will be left. For this we use the above formula.
120 grams will be left after 180 years.
Answer:
Step-by-step explanation:
Since Gloria cannot pay for each minute talked but for packages of 200 minutes at the rate of $25 each, we have to make calculations according to these conditions as follows:
Month 1:
Gloria talked on her cell phone for . So, she had to buy 2 packages of
for
each package.
Hence:
Month 2:
Gloria talked on her cell phone for . So, she had to buy again 2 packages of
for
each package.
Hence:
Month 3:
Gloria talked on her cell phone for . So, she had to buy 3 packages of
for
each package.
Hence:
Then, if we take the total Gloria had to pay for the frist three months, we have: