The sum of 8 and 7 doubled
2 answers:
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The sum of the first n odd numbers is n squared! So, the short answer is that the sum of the first 70 odd numbers is 70 squared, i.e. 4900.
Allow me to prove the result: odd numbers come in the form 2n-1, because 2n is always even, and the number immediately before an even number is always odd.
So, if we sum the first N odd numbers, we have
The first sum is the sum of all integers from 1 to N, which is N(N+1)/2. We want twice this sum, so we have
The second sum is simply the sum of N ones:
So, the final result is
which ends the proof.
Answer:
0.03125
Step-by-step explanation:
If we have a fair coin the probability of landing a head is 50%.
We can think the question as what is the probability of landing four tails and then a head. That is we needed at least 5 tries to get a head.
Since this events are independent we can write it as