Algebra II quiz

JavaScript with alert box only (no AJAX or C#).

1.) What can we say about the first term in an arithmetic series?
  It is always 1.
  It cannot be 4.
  It cannot be 10.
  It can be any number!

2.) An arithmetic series has t1=1, tn=11, n=11. What is its sum?
  Not enough information - what is d?
  110
  55
  66

3.) An arithmetic series has t1=1, d=4, n=11. What is its sum?
  40
  440
  231, since tn = 1+(10*4) = 41.
  Unknown, since we don't know tn

4.) An arithmetic series has t1=1, tn=49, n=10. What is its sum?
  500
  250
  275
  Unknown, since we don't know d

5.) An arithmetic series has d=2, tn=50, n=10. What is its sum?
  390
  820
  410, since t1=tn-9*2=50-18=32.
  Unknown, since we don't know t1

6.) An arithmetic series has t1=32, d=2, tn=50. What is its sum?
  390
  820
  410 (tn-t1=(n-1)*d->50-32=(n-1)*2->n=10)
  Unknown, since we don't know n