The initial fee for a gym membership is $10 and for each month of the membership it costs $5. Jem has been going to the gym for 8 months, what is the total cost?
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Answer: 28</h3>
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Explanation:
Method 1
Imagine a table with 8 rows and 8 columns to represent all possible match-ups. You can actually draw out this table or just think of it as a thought experiment.
There are 8*8 = 64 entries in the table. Along the northwest diagonal, we have each team pair up with itself. This is of course silly and impossible. We cross off this entire diagonal so we drop to 64-8 = 56 entries.
Then notice that the lower left corner is a mirror copy of the upper right corner. A match-up like AB is the same as BA. So we must divide by 2 to get 56/2 = 28 different matches.
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Method 2
There are 8 selections for the first slot, and 8-1 = 7 selections for the second slot. We have 8*7 = 56 permutations and 56/2 = 28 combinations.
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Method 3
Use the nCr combination formula with n = 8 and r = 2

There are 28 combinations possible. Order doesn't matter (eg: match-up AB is the same as match-up BA).
Notice how the (8*7)/2 expression is part of the steps shown above in the nCr formula.
Answer: Gustavo is 261.96 meters away from Aiden. Or Aiden is 261.96 meters away from Gustavo.
Step-by-step explanation: From the question, considering a North, East, South and west pole, Gustavo ran 23° above the east horizontal, while Aiden ran 33° below the east horizontal.
Therefore, Where a and b are distances travelled respectively by Gustavo and Aiden. While θ is the angle between them.the total angle between them is 23 + 33 = 56°. Therefore, let the distance between them be c and we can calculate that using the cosine law.c² = a² + b² – 2ab cos θ. Therefore, let the distance between them be c and we can calculate that using the cosine law.c² = a² + b² – 2ab cos θ.
Therefore, they are 261.96 meters apart.
c² = 300² + 250²– 2(300) (250)cos 56
c² = 90000 + 62500 - 83878.9355
c² = 68621.0645
c = √68621.0645
c = 261.96 m