Answer:
D. 15P15 * 10P5
Step-by-step explanation:
Since you have to place all first-grade students in the first three rows, and nowhere else, we have to make a special calculation for that, then another for the rest of the bus.
These are permutations since the order is important. If we sit John, Paul, Ringo, George and Pete in this order in the first row it's a different way than seating them (in the same order) in the second row for example.
For the 15 first-graders of the first three rows (15 seats), we have 15P15 since all 15 places have to be occupied by all 15 first-graders.
Then we have 10 remaining seats left to be assigned to the 5 second-graders. That is 10P5.
We then multiply the permutation numbers of those two arrangements to get the total ways:
15P15 * 10P5, answer D.
<span>x-y=192 or x=192+y
y=x/5 now replace y with (x/5) in the first equation & solve for x
x=192+x/5
x-x/5=192
4x/5=192 cross multily
4x=5*192
4x=960</span>
Try using polar expression forms. z = r(cos theta + sin theta) as well as x = r cos theta and y = r sin theta. Plug in the values you have. x = 4 cos 120 or 2pi/3 and solve. Do the same for y = 4 sin 120 or 2pi/3. It will give the "x" and "y" parts of your rectangular coordinates.
