The formula for an arithmetic sequence is An=A1+(n-1)d.
Using this knowledge, you can set up the equation easily to be An=1+(12-1)-5
You then simplify this to 1-55 using PEMDAS, giving you the answer for the twelfth term being -54, you then do this for every term if you want (or you could just subtract 5 by the terms after 14 till you get to -54. After all that, you add the twelve terms up to get -319 as your final answer
You can’t really answer this without showing us the the answer you got from item 6
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.
The answer to this question is they both have 0s
