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HELP ASAP PLZ !!!!!!!!!

HELP ASAP PLZ !!!!!!!!!-example-1

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Answer:

1. n=3 Sum=60

2. n=6 sum=411

3. n=9 sum= 238.5

Step-by-step explanation: use the formula n( a1+A)

Ex: 3(19+21/2)= 60

n is the amount of numbers you have.

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