By Sixtoes (Sixtoes) on Monday, May 26, 2003 - 12:42 pm: Edit

If the 20th term of an arithmetic sequence is 100 and the 40th term of the sequence is 250, what is the first term of the sequence?
A) -50
B) -42.5
C) 5
D) 42.5
E) 50

I got (B) as my answer, but supposedly (C) is correct. How?

If n distinct planes intersect in a line, and another line l intersects one of these planes in a single point, what is the /least/ of these n planes that l could intersect?
A) n
B) n-1
C) n-2
D) n/2
E) (n-1)/2

I got (A) but the answer is supposed to be (B).

Thanks so much!

 By Wharton1986 (Wharton1986) on Monday, May 26, 2003 - 03:30 pm: Edit

the answer to the first question is option number be(-42.5)

u use the formula tn=a+(n-1)d.

and solve the equations simultaneosly.

yup b is correct ..the book(i guess barrons sux ) and they gave u the wrong answer..happens a lot.

about the second 1..im really bad at the whole plane thing but if i were answering i would prolly write a.

hope this helps.

 By Peanuts (Peanuts) on Monday, May 26, 2003 - 05:09 pm: Edit

under what conditions is xy/(x-y) negative?

A. 0<x<y
B.x<y<0
C.y<0<x
D.y<x<0
E. none of above

i got both A and C when book says C. typo right?

 By Rubenizm (Rubenizm) on Monday, May 26, 2003 - 05:52 pm: Edit

i think so

 By Hahaha (Hahaha) on Monday, May 26, 2003 - 05:54 pm: Edit

yep, it would be both A and C. I guess it's a typo.

 By Pat57575 (Pat57575) on Monday, May 26, 2003 - 06:28 pm: Edit

Okay, the hardest part about the 2nd problem is visualizing it. Try to imagine many infinitely extending planes all intersecting on a single line. Now, if you were to choose any point on any one of these planes, and you were to draw a line through it extending in any direction(remember also, lines extend infinitely), it would intersect every other plane EXCEPT the plane (assuming it exists) whose surface is parallel to the line. If such a parallel plane exists the line will intersect n-1 planes, and if there is no parallel plane the line will interect n planes. B/C it asks for the lowest possibility, 'n-1' is the correct choice.

 By Andrew123s (Andrew123s) on Monday, May 26, 2003 - 10:54 pm: Edit

under what conditions is xy/(x-y) negative?

A. 0<x<y
B.x<y<0
C.y<0<x
D.y<x<0
E. none of above"

Yeah, I got A and C (I just did that Barron's test today).