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The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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13 Dec 2015, 05:07
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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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13 Dec 2015, 05:27
Bunuel wrote: The youngest of 4 children has siblings who are 3, 5, and 8 years older than she is. Let age of the youngest child be " y " Age of the all the children in the family is y , (y + 3) ,(y + 5) and (y + 8) Total age of all the children in the family is y + (y + 3) + (y + 5) + (y + 8) => 4y + 16 Bunuel wrote: If the average (arithmetic mean) age of the 4 siblings is 21, what is the age of the youngest sibling? Total age of the 4 sibling is 21 x 4 = 84 years .. We already have the total age of alll the children is 4y + 16 So, 4y + 16 = 84 Or, 4y = 68 Or, y = 17 So, Age of the youngest child is 17 years.
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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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13 Dec 2015, 11:16
let the youngest be Y sum of ages of all the children = 4y+16=4*(avg) 4y+16=84 y=17



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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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14 Dec 2015, 16:57
Hi All, This question can be solved by TESTing THE ANSWERS. We're told that the YOUNGEST of 4 children has siblings who are 3, 5, and 8 years OLDER than she is and that the average age of the 4 siblings is 21. We're asked for the age of the youngest sibling. Since the average age is 21 and we're trying to figure out the age of the YOUNGEST sibling, we should look for an answer that is several years LESS than 21... Let's TEST Answer B: 18 years IF... Youngest = 18 Siblings = 21, 23 and 26 Sum = 88 Average = 88/4 = 22 This is TOO HIGH (the average is supposed to be 21). Since the average is too high, all 4 of the children are TOO OLD. There's only one answer left that would lower the average... Final Answer: GMAT assassins aren't born, they're made, Rich
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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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15 Dec 2015, 11:45
Testing the answer in my opinion takes a long time.
We know that each one is 3,5,8 years OLDER
X + (3+X) + (5+X) + (8+X) = 21*4 4X + 16 = 84 4X = 68 X = 17



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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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15 Dec 2015, 15:55
Hi douglasvg, If you're not using Tactics (such as TEST THE ANSWERS) very often, then it might take you a little longer to use that approach right now (since you're not used to thinking in that way). However, in the long run  and on harder questions  those same Tactics can be extremely valuable. 1) How have you been scoring on your practice CATs (including the Quant and Verbal Scaled Scores)? 2) How is your pacing in the Quant section? Do you have to rush just to finish? GMAT assassins aren't born, they're made, Rich
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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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15 Dec 2015, 16:06
EMPOWERgmatRichC wrote: Hi douglasvg,
If you're not using Tactics (such as TEST THE ANSWERS) very often, then it might take you a little longer to use that approach right now (since you're not used to thinking in that way). However, in the long run  and on harder questions  those same Tactics can be extremely valuable.
1) How have you been scoring on your practice CATs (including the Quant and Verbal Scaled Scores)? 2) How is your pacing in the Quant section? Do you have to rush just to finish?
GMAT assassins aren't born, they're made, Rich On GMATPREP software Im scoring between 4550 in quant For hard question I indeed use it, then its a fast way to solve it. Thank you Empower



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The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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09 Jan 2018, 09:12
Bunuel wrote: The youngest of 4 children has siblings who are 3, 5, and 8 years older than she is. If the average (arithmetic mean) age of the 4 siblings is 21, what is the age of the youngest sibling?
A. 17 B. 18 C. 19 D. 21 E. 22 Let y = the age of the youngest child So, y + 3 = age of sibling who is 3 years older than the youngest child y + 5 = age of sibling who is 5 years older than the youngest child y + 8 = age of sibling who is 8 years older than the youngest child The average (arithmetic mean) age of the 4 siblings is 21This means: [y + (y+3) + (y+5) + (y+8)]/4 = 21 Multiply both sides by 4 to get: y + (y+3) + (y+5) + (y+8) = 84 Simplify: 4y + 16 = 84 Solve: y = 17 Answer: A Cheers, Brent
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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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10 Jan 2018, 00:31
X + (3+X) + (5+X) + (8+X) = 21*4 4 X + 16 = 84 4 X = 68 X = 17



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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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30 Jul 2018, 10:33
Bunuel wrote: The youngest of 4 children has siblings who are 3, 5, and 8 years older than she is. If the average (arithmetic mean) age of the 4 siblings is 21, what is the age of the youngest sibling?
A. 17 B. 18 C. 19 D. 21 E. 22 We can let x = the age of the youngest child; thus, the ages of the three older children are x + 3, x + 5 and x + 8, respectively. We can create the equation: (x + x + 3 + x + 5 + x + 8)/4 = 21 4x + 16 = 84 4x = 68 x = 17 Answer: A
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Re: The youngest of 4 children has siblings who are 3, 5, and 8 years olde
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21 Nov 2018, 08:45
If the average age of the 4 siblings is 21, we can determine the sum of ages by reversing division by 4.
\(\frac{x}{4}= 21\) \(x = 4*21\) \(x = 84\)
From there, we can set up an equation to find the age of the youngest child based on their age relative to their siblings.
If the youngest child = x:
\(x + (x+3) + (x+5) + (x+8) = 84\) \(4x + 16 = 84\) \(4x = 68\) \(x = 17\)
Therefore, the youngest child is 17 (option A).




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