Danielle went ice skating. It cost $3 an hour and $5 for skate rental. If Danielle spent $11, how many hours did she ice-skate?
1 answer:
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Part A:
The amount of substance left of a radioactive substance with a half life
and amount of initial substance 
is given by
Given that th<span>e isotope samarium-151 has a half-life of around 96.6 years and the rock contains 5 grams of samarium-151 when it reaches its closure temperature, and it contains 0.625 grams when it is discovered.
</span><span>The time since the rock reached its closure temperature is obtained as follows:
Therefore, </span>t<span>he time since the rock reached its closure temperature is 289.8 years.
Part B:
Given that the </span><span>rock contains 5 grams of samarium-151 when it reaches its closure temperature, and it contains 0.625 grams when it is discovered. The number of grams of europium-151 when the rock was discovered is 5 - 0.625 = 4.375</span>
The amount of substance left of a radioactive substance with a half life
Given that th<span>e isotope samarium-151 has a half-life of around 96.6 years and the rock contains 5 grams of samarium-151 when it reaches its closure temperature, and it contains 0.625 grams when it is discovered.
</span><span>The time since the rock reached its closure temperature is obtained as follows:
Therefore, </span>t<span>he time since the rock reached its closure temperature is 289.8 years.
Part B:
Given that the </span><span>rock contains 5 grams of samarium-151 when it reaches its closure temperature, and it contains 0.625 grams when it is discovered. The number of grams of europium-151 when the rock was discovered is 5 - 0.625 = 4.375</span>