Molly bought gas for 11.50 for 4 gallons how much did each gallon
2 answers:
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Answer:
300
Step-by-step explanation:
There are 25 ways to select the first student. After that student is removed from the selection pool for the second student, there are 24 ways to select the second student. This gives 25·24 = 600 ways to select 2 students <em>in a particular order</em>.
Since we don't care about the order, we can divide this number by the number of ways two students can be ordered: AB or BA, 2 ways.
600/2 = 300
There are 300 ways to pick a combination of two students from 25.
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<em>Additional comments</em>
This sort of selection (2 out of 25) has a formula for it, and an abbreviation for the formula.
"n choose k" can be written nCk or C(n, k)
The function is a ratio of factorials:
nCk = n!/(k!(n-k)!)
If you can typeset this, it is written ...
This is different from the formula for the number of <em>permutations</em> of n things taken k at a time. That would be written nPk or P(n, k) = n!/(n-k)!.
For the ODE
multiply both sides by <em>t</em> so that the left side can be condensed into the derivative of a product:
Integrate both sides with respect to <em>t</em> :
Divide both sides by to solve for <em>y</em> :
Now use the initial condition to solve for <em>C</em> :
So the particular solution to the IVP is
or