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Math SAT Problems

sat2014sat2014 Registered User Posts: 495 Member
Hi, I'm stuck on problems 8 13 16 and 20 on section 4. If someone can please explain how to do them, I'd appreciate it. thank you! https://app.box.com/s/xbyk2msfo80hmha47b2p

Replies to: Math SAT Problems

  • sat2014sat2014 Registered User Posts: 495 Member
    https://app.box.com/s/xbyk2msfo80hmha47b2p Section 7 problems 5 7 8 16 17 and 18 I'm lost. please help if you can. thanks!
  • bvo112bvo112 Registered User Posts: 298 Junior Member
    13 on section 4 is D... y^10 is the same as (y^5)^2 = 50^2 = 2500... then z^-2 is the same as (z^2)^-1 = (10)^-1 which is 1/10. So if you multiply 1/10 by 2500 you get 250 which is C.

    8 on section 7 is E

    16 on section 7 - Since (5,7) is the center, and Point O and P are on the circle, the distance from center to O is the same as distance from center to P. O has a point (0, 0) so distance formula. Use the distance to get the y coordinate of P since you know the x-component of P is 0.
  • MITer94MITer94 Registered User Posts: 4,747 Senior Member
    Section 4
    8: ST = OR, and we know that R = (-3,0), and ST = 3. SInce ST = 3OR, OR = 1, and since S is in the second quadrant, k = 1. C

    16: ∠A = 50 (deg) since triangle ABC is a right triangle. AB = BD, so ∠A = ∠ADB = 50 --> ∠ABD = 80 --> x = 90 - ∠ABD = 90 - 80 = 10 degrees. A

    20. I rarely use this strategy, but plugging in numbers works well here. If n = -10, for example, the choices are: -1/100, 1/100, -1/10, -1/11, -1/9. Of these choices, -1/9 has the least value, so the answer is E.

    Section 8
    5: 5 "pens" = 2000 cartons of pens (by reading the pictograph/question) so one pen = 400 cartons. Number of type Z cartons is 10*400 = 4000 cartons.

    7: You have to draw this one out visually and see. Answer is C.

    17: 3+5+7 = 15, which is not prime. 17 cannot be written as a sum of three different primes. 19 can only be written as 3+5+11, and 3*5*11 = 165. 23 starts getting much bigger, and the best solution is n = 3*5*11 = 165.

    18. Let b = price of ground beef per lb, and n = # of pounds of ground beef bought. Then the cost of coffee (per pound) is 2b and the number of pounds of coffee bought is n/3. Then we have

    bn + (2b)(n/3) = 9.60
    bn + (2/3)bn = 9.60

    We see that coffee accounted for 2/5 of the total cost since (2/3)/(1 + 2/3) = 2/5, so the cost of the coffee is 9.60*(2/5) = 3.84.



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