## hba 2 years ago Stats help required

1. hba

2. saifoo.khan

$mean = \frac{\sum fx}{\sum x}$

3. wio

ah, so it's just a weighted average.

4. kropot72

Solve the following for x: $\frac{12(x-5)+40x+8(x+5)}{60}=10$

5. hba

Whatt is the general formula @kropot72

6. ParthKohli

$\dfrac{\underbrace{x - 5 + x - 5 \cdots+ x-5}_{\rm 12 ~times} + \underbrace{x + x\cdots x + x}_{\rm 40 ~ times} + \underbrace{x + 5 +\cdots+ x+5}_{\rm 8 ~times}}{12 + 40 + 8}$

7. hba

Thanks a lot but there would be some general form of this :/

8. hba

@Mimi_x3

9. saifoo.khan

I wrote the general formula already.

10. hba

Shouldnt it be, $\sum_{}^{}fx/\sum_{}^{}f$

11. hba

Next.

12. saifoo.khan

$Arithmetic => \frac{x+y}{2} = 10.2$

13. hba

14. saifoo.khan

Geo mean formula: √(xy)

15. hba

Sqrt(x*y)

16. hba

Okay got it

17. saifoo.khan

$√(xy) = 8.4$

18. hba

Do i have to solve quad equations?

19. saifoo.khan

take square on both sides: xy = sqrt8.4 x = sqrt(8.4)/y

20. hba

I know that

21. saifoo.khan

Now substitute this in the first equation

22. hba

But it would be x=70.56/y

23. saifoo.khan

o_O

24. hba

Whut?

25. hba

sqrt(xy)=8.4 xy=70.56 x=70.56/y

26. saifoo.khan

Oh right.

27. saifoo.khan

Actually i'm doing two things at once. XD

28. hba

No worries c:,This thing is going into a quad equation :(

29. saifoo.khan

Go for it

30. hba

x=77.16,-56.76 and y=77.16,-56.76

31. hba

I feel like i have made a mistake :/

32. saifoo.khan

Let me check.

33. hba

Should i do it again?

34. saifoo.khan

x = 4.41, y = 15.99 x = 15.99, y = 4.41

35. hba

Lemme do it again,Stop playing with wolf :/

36. mathslover

may i help?

37. hba

No thanks

38. mathslover

39. mathslover

if you're completed with your soln

40. hba

I will

41. hba

Okay x=15.98,4.414 and y=4.414,15.98

42. saifoo.khan

great.

43. hba

Now next question, I am getting b=2,b=8 and a=8,a=2

44. hba

So harmonic mean is 16/5=3.2

45. hba

Right @saifoo.khan ?

46. saifoo.khan

Never heard of harmonic mean. :s

47. hba

Okay lets call someone else for that case,What about the observation do you think they are right? Btw,A.M is opposite of H.M.

48. mathslover

I cn help in HM

49. hba

And, H.M=N/(1/a1+1/a2+......1/an)

50. hba

@mathslover Do you think my answers are correct?

51. mathslover

lemme check tht .. wait

52. hba

Okay

53. mathslover

yep u r right

54. mathslover

great work

55. hba

Thanks but now i want to ask, As i have two diff observations a=8,b=2 and a=2,b=8 and the HM is same so should i show this two times?

56. mathslover

yes you have to mention that it will be same in both cases

57. hba

Okay now next question.

58. hba

Wait a sec

59. hba

60. saifoo.khan

Namaz parhlo.

61. hba

Chalo okay namaz kai baad krtai hai.

62. hba

Han continue karlain @saifoo.khan

63. hba

@AravindG Can you help?

64. AravindG

sorry I am a really busy ...

65. hba

I am really busy*

66. hba

@saifoo.khan I am waiting :/

67. hba

68. hba

@hartnn See the last attachment

69. hartnn

same weighted average formula.

70. hartnn

(700*8.5+800*7.5+500*8)/2000

71. hartnn

$$\sum_{}^{}fx/\sum_{}^{}f$$

72. hba

I was thinking about using this but i am not getting why is sum of f=2000

73. hartnn

sum of f = 700+800+500

74. hba

Okay thanks :)

75. hba

I am getting mean=7.85,Am i right? @mathslover

76. hba

@hartnn

77. hartnn
78. hba

Close enough lol :P I am using a casio scientific calculator,I dont know why it rounded the answers :/

79. hba

Oh yeah i checked it again,Its 7.95 thanks. I have another question may i ask? @hartnn

80. hartnn

yes

81. hba

Okay here we go :D

82. hartnn

you tried ?

83. hba

Wait wait dont answer i am trying

84. hba

$\sum_{i=1}^{n}a_i=16.2$ Okay @hartnn Please explain