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If the temperature readings at noon for three consecutive days are +9°

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If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 13 Oct 2017, 00:25
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If the temperature readings at noon for three consecutive days are +9°,—6°, and +8°, what must the reading be at noon on the fourth day for the average (arithmetic mean) noon temperature of all four days to be +4°?

A. –11°
B. –7°
C. +2°
D. +4°
E. +5°

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Re: If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 13 Oct 2017, 00:28
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D) +5degree... solution:- +9-6+8+4/4...The result is +4 degree which is the average (arithmetic mean)

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Re: If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 13 Oct 2017, 00:29
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bandanah wrote:
D) +5degree... solution:- +9-6+8+4/4...The result is +4 degree which is the average (arithmetic mean)

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9-6+8+5/4...it's +5 and not +4.

Bunuel wrote:
If the temperature readings at noon for three consecutive days are +9°,—6°, and +8°, what must the reading be at noon on the fourth day for the average (arithmetic mean) noon temperature of all four days to be +4°?

A. –11°
B. –7°
C. +2°
D. +4°
E. +5°



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Re: If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 13 Oct 2017, 00:36
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Let the temperature of the 4th day be: x

\(\frac{+9-6+8+x}{4}\) =4

11+x=16
x= 16-11= +5

Answer: E.

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Re: If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 13 Oct 2017, 01:32
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Let the temperature of the 4th day be: x

+9−6+8+x4+9−6+8+x4 =4

11+x=16
x= 16-11= +5

Answer: E.
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Re: If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 13 Oct 2017, 06:20
Bunuel wrote:
If the temperature readings at noon for three consecutive days are +9°,—6°, and +8°, what must the reading be at noon on the fourth day for the average (arithmetic mean) noon temperature of all four days to be +4°?

A. –11°
B. –7°
C. +2°
D. +4°
E. +5°



best way => you want 4 as average=> compare wrt 4 up or down
9 = u went 5 up
-6 = u went 10 down => 5 down nett
+8 = u went 4 up => 1 down nett
assume 4th one be 4 so if u take 4 => u are still 1 down in nett
to raise by 1 you should have 5 in th place so that when 5 is there 1 up will nullify 1 down

=> 4 is avg when => 5 is the answer

==========================

9 is 5 higher
-6 is 10 lower ( net 5 lower)
8 is 4 higher ( net 1 lower)
5 is 1 higer ( net same )

5 is answer
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Re: If the temperature readings at noon for three consecutive days are +9°  [#permalink]

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New post 27 Nov 2017, 19:12
Bunuel wrote:
If the temperature readings at noon for three consecutive days are +9°,—6°, and +8°, what must the reading be at noon on the fourth day for the average (arithmetic mean) noon temperature of all four days to be +4°?

A. –11°
B. –7°
C. +2°
D. +4°
E. +5°


We can let n = the temperature on the fourth day and use the formula sum/number = average to create the equation:

(9 + (-6) + 8 + n)/4 = 4

11 + n = 16

n = 5

Answer: E
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Re: If the temperature readings at noon for three consecutive days are +9° &nbs [#permalink] 27 Nov 2017, 19:12
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