Two cards are drawn one at a time from a full deck of cards. a) What’s the probability they are an ace or a heart? b) What’s the
1 answer:
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Answer:
He should have multiplied both numbers by 100
Step-by-step explanation:
Given
See Attachment for given
Required
What's Chen error
Chen error is at step 2 where he changed 0.9 to 9.
Any changes made on the divisor must also be made on the dividend
He got 9 by multiplying 0.9 by 10;
So, his mistake is that he should have multiplied both numbers by the same number.
From the list of given options, the option that best answer this question is He should have multiplied both numbers by 100
Answer:
20,944 years
Step-by-step explanation:
The formula you use for this type of decay problem is the one that uses the decay constant as opposed to the half life in years. We are given the k value of .00012. If we don't know how much carbon was in the bones when the person was alive, it would be safer to say that when he was alive he had 100% of his carbon. What's left then is 8.1%. Because the 8.1% is left over from 100% after t years, we don't need to worry about converting that percent into a decimal. We can use the 8.1. Here's the formula:
where N(t) is the amount left over after the decay occurs, is the initial amount, -k is the constant of decay (it's negative cuz decay is a taking away from as opposed to a giving to) and t is the time in years. Filling in accordingly,
Begin by dividing the 100 on both sides to get
Now take the natural log of both sides. Since the base of a natual log is e, natural logs and e "undo" each other, much like taking the square root of a squared number.
ln(.081)= -.00012t
Take the natual log of .081 on your calculator to get
-2.513306124 = -.00012t
Now divide both sides by -.00012 to get t = 20,944 years