Page 1 of 2 12 LastLast
Results 1 to 20 of 22

Thread: SAT math problem

  1. #1
    Rookie
    Join Date
    Feb 2007
    Location
    Trumbull, CT
    Posts
    859

    SAT math problem

    Okay this problem is killing me because i couldnt figure it out from the sat i took on saturday. can anybody help.
    There are three circles. The sum of their areas equals pi. The second circles radius is equal to 1/2 of the first and the third is 1/3.
    So using A=(pi)r^2
    Pi= (pi)r^2 + (pi) (1/2r)^2) + (pi)(1/3r)^3)
    So you factor out the pi and divide by pi to get
    1=r^2 + (1/2r)^2 + (1/3r)^2
    Now i know it would be a lot easier with the multiple choice answers and you could just plug them in, but I forgot them and ran out of time to simply plug them in and this problem is killing me.
    All help is appreciated

  2. #2
    [img]http://www.mexicanglowworm.com/Assets/Images/picofweek/rodneydangerfield.jpg[/img]

    The answer is... four?

  3. #3
    All League
    Join Date
    Oct 2007
    Location
    It's all relative
    Posts
    4,069
    r=0.857? plus or minus?

  4. #4
    [QUOTE=CTJetFan92;3303314]Okay this problem is killing me because i couldnt figure it out from the sat i took on saturday. can anybody help.
    There are three circles. The sum of their areas equals pi. The second circles radius is equal to 1/2 of the first and the third is 1/3.
    So using A=(pi)r^2
    Pi= (pi)r^2 + (pi) (1/2r)^2) + (pi)(1/3r)^3)
    So you factor out the pi and divide by pi to get
    1=r^2 + (1/2r)^2 + (1/3r)^2
    Now i know it would be a lot easier with the multiple choice answers and you could just plug them in, but I forgot them and ran out of time to simply plug them in and this problem is killing me.
    All help is appreciated[/QUOTE]

    You do recognize that these are JET fans you are talking to correct???

    We do not make up the top 5 percentile of achivers on written exams or so I would imagine.

    That said, I have NO idea????

    My best advice is to understand that you will NOT score 100 percent and accept the fact that THIS question is one of the wrong ones and lose NO SLEEP over it. The fact that it bothers you tells me you are probably one of the top performers on the exam anyway.

    Best of Luck!!!

    What college are you considering?
    Last edited by southparkcpa; 10-12-2009 at 12:59 PM.

  5. #5
    Board Moderator
    Join Date
    Sep 2005
    Location
    Brooklyn Heights
    Posts
    2,462
    [QUOTE=CTJetFan92;3303314]Okay this problem is killing me because i couldnt figure it out from the sat i took on saturday. can anybody help.
    There are three circles. The sum of their areas equals pi. The second circles radius is equal to 1/2 of the first and the third is 1/3.
    So using A=(pi)r^2
    Pi= (pi)r^2 + (pi) (1/2r)^2) + (pi)(1/3r)^3)
    So you factor out the pi and divide by pi to get
    1=r^2 + (1/2r)^2 + (1/3r)^2
    Now i know it would be a lot easier with the multiple choice answers and you could just plug them in, but I forgot them and ran out of time to simply plug them in and this problem is killing me.
    All help is appreciated[/QUOTE]



    [url]http://www.youtube.com/watch?v=e2gnu1WXQk0[/url]

  6. #6
    Veteran
    Join Date
    Apr 2007
    Location
    Auburn, Indiana, United States
    Posts
    1,342

    I know somebody that can help!

    [IMG]http://i210.photobucket.com/albums/bb311/fuzzy1729/GoodWillHuntingMath.jpg[/IMG]

  7. #7
    You never said what you were solving for.

    If it was for the radius of the big circle, the answer would be 6/7. You'd solve it the way you wrote, remembering the exponent went to the fraction as well as the variable.

    Other than that, you'd have to remember what the actual question was.

  8. #8
    All League
    Join Date
    Feb 2005
    Location
    Long Island, NY
    Posts
    3,519
    [QUOTE=CTJetFan92;3303314]Okay this problem is killing me because i couldnt figure it out from the sat i took on saturday. can anybody help.
    There are three circles. The sum of their areas equals pi. The second circles radius is equal to 1/2 of the first and the third is 1/3.
    So using A=(pi)r^2
    Pi= (pi)r^2 + (pi) (1/2r)^2) + (pi)(1/3r)^2)
    So you factor out the pi and divide by pi to get
    [B]1=r^2 + (1/2r)^2 + (1/3r)^2[/B]
    Now i know it would be a lot easier with the multiple choice answers and you could just plug them in, but I forgot them and ran out of time to simply plug them in and this problem is killing me.
    All help is appreciated[/QUOTE]

    1=r^2 + (1/2r)^2 + (1/3r)^2

    up to here is good.

    next you have:
    1 = r^2 + (1/4) r^2 + (1/9) r^2

    then

    1 = r^2 (1 + 1/4 + 1/9)

    then

    1 = r^2 (36/36 + 9/36 + 4/36)

    1 = r^2 (49/36)

    36/49 = r^2

    r1 = 6/7, r2 = 3/7, r3 = 2/7

    no calulcator needed

  9. #9
    The third circle's R=(1/3) of the first circle's R?

    R= .7386 (the square root of 1/1.833)

    plug it in - it works

  10. #10
    Veteran
    Join Date
    Feb 2009
    Location
    Brooklyn
    Posts
    2,286
    you will never get into college now.

  11. #11
    [QUOTE=loluchka80;3303479]1=r^2 + (1/2r)^2 + (1/3r)^2

    up to here is good.[/QUOTE]

    or just go:

    1 = (r^2) (1 + .5 + .333)

    1 = (r^2) (1.833)

    1/1.8333 = r^2

    sq root of .54546 = r

    r = .73855 rounded

  12. #12
    All League
    Join Date
    Feb 2005
    Location
    Long Island, NY
    Posts
    3,519
    [QUOTE=jetsNOW!;3303534]or just go:

    1 = (r^2) (1 + .5 + .333)

    1 = (r^2) (1.833)

    1/1.8333 = r^2

    sq root of .54546 = r

    r = .73855 rounded[/QUOTE]

    the answer was probably 6/7 though. i just wanted to show CTJetFan that you can do all the problems on the SAT without a calculator.

    it gets too complicated when you start plugging long decimal numbers into your calculator. leave everything in fraction form, it's no coincidence that the answer is the square root of 36 over 49 (two perfect squares).

  13. #13
    Hall Of Fame
    Join Date
    Jan 2006
    Location
    Long Island & Section 337
    Posts
    4,859
    [QUOTE=ListerFiend;3303515]you will never get into college now.[/QUOTE]

    What ever happened with you and the Latin professor? Did you transfer?

  14. #14
    All League
    Join Date
    Oct 2007
    Location
    It's all relative
    Posts
    4,069
    [QUOTE=OCCH;3303468]If it was for the radius of the big circle, the answer would be [B]6/7[/B]. You'd solve it the way you wrote, remembering the exponent went to the fraction as well as the variable.[/QUOTE]

    That's what I said, 0.857!

    [QUOTE=loluchka80;3303479]1=r^2 + (1/2r)^2 + (1/3r)^2

    up to here is good.

    next you have:
    1 = r^2 + (1/4) r^2 + (1/9) r^2

    then

    1 = r^2 (1 + 1/4 + 1/9)

    then

    1 = r^2 (36/36 + 9/36 + 4/36)

    1 = r^2 (49/36)

    36/49 = r^2

    r1 = [B]6/7[/B], r2 = 3/7, r3 = 2/7

    no calulcator needed[/QUOTE]

    That's what I said, 0.857! Jeez, where's the credit?!

    [QUOTE=jetsNOW!;3303509]The third circle's R=(1/3) of the first circle's R?

    R= .7386 (the square root of 1/1.833)

    plug it in - it works[/QUOTE]

    No, .7386 doesn't quite work.

  15. #15
    All League
    Join Date
    Feb 2005
    Location
    Long Island, NY
    Posts
    3,519
    [QUOTE=Big L;3303601]That's what I said, 0.857!
    That's what I said, 0.857! Jeez, where's the credit?!
    [/QUOTE]

    you just gave him the answer with no work. i was trying to show him how to get it.

    also, i bet none of the choices were 0.857. it was most likely 6/7. a calculator is unnecessary for the SAT.

  16. #16
    [QUOTE=Big L;3303601]That's what I said, 0.857!



    That's what I said, 0.857! Jeez, where's the credit?!



    No, .7386 doesn't quite work.[/QUOTE]

    See now that I separated the r^2's from the quantity^2 without squaring the fractions. Knew I should've done it on paper first using clearer notation than my keyboard allows. Any more? That was fun, haven't tried one of those in many years

  17. #17
    Board Moderator
    Jets Insider VIP

    Join Date
    Jul 2003
    Location
    NYC
    Posts
    19,374
    Damn...I did really well on my math SAT and none of that looks even remotely familiar.

    Granted it was well over 15 years ago, but still.

  18. #18
    All League
    Join Date
    Oct 2007
    Location
    It's all relative
    Posts
    4,069
    [QUOTE=loluchka80;3303649]you just gave him the answer with no work. i was trying to show him how to get it.

    also, i bet none of the choices were 0.857. it was most likely 6/7. a calculator is unnecessary for the SAT.[/QUOTE]

    [QUOTE=jetsNOW!;3303655]See now that I separated the r^2's from the quantity^2 without squaring the fractions. Knew I should've done it on paper first using clearer notation than my keyboard allows. Any more? That was fun, haven't tried one of those in many years[/QUOTE]

    I'm just breakin stones. :D

  19. #19
    Veteran
    Join Date
    Feb 2009
    Location
    Brooklyn
    Posts
    2,286
    [QUOTE=HDCentStOhio;3303560]What ever happened with you and the Latin professor? Did you transfer?[/QUOTE]

    no, i'm able to keep my scholarship, but the case is still pending for the grade on my transcript.

  20. #20
    Here's a math problem I went through the other day with the girl working the McDonald's drive-thru. I placed an order which came to $7.61. I payed with a $20.00 bill. When the register opened she said is it ok I don't have any pennies. Remembering that the total ended in a 1, I said tha's OK and gave her a single penny from my ashtray which is filled with change. She responded with a perplexed expression and said, "Now I don't know how much change to give you." Resisting the urge to state, "Kill Yourself", I asked her how much change the register indicated. She responded $12.39. I then had to tell her that the proper change was $12.40. Solve for Y was she the one they put on the register and what does that say about the rest of the people working there.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Follow Us