What is the average (arithmetic mean ) of j and k?
1) the average of j+k and k+4 is 11
2) the average of j,k and 14 is 10
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data sufficiency
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romitvsingh
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shankar.ashwin
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(j+k)/2 is the average, so if we can find (j+k) we can find the average.
Statement 1:
[(j+k) + (k+4)]/2 = 11
j+2k+4 = 22
j+2k = 18 - we cannot find j+k from this - Insufficient
Statement 2:
j+k+14/3 = 10
j+k+14 = 30
J+k = 16 - sufficient - B IMO
Statement 1:
[(j+k) + (k+4)]/2 = 11
j+2k+4 = 22
j+2k = 18 - we cannot find j+k from this - Insufficient
Statement 2:
j+k+14/3 = 10
j+k+14 = 30
J+k = 16 - sufficient - B IMO
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GMATGuruNY
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For those who would struggle with the algebra, an alternate approach is to plug in values.romitvsingh wrote:What is the average (arithmetic mean ) of j and k?
1) the average of j+k and k+4 is 11
2) the average of j,k and 14 is 10
Try two cases.
If the average of j+k is the same in each case, the statement is SUFFICIENT.
If the average of j+k changes, the statement is INSUFFICIENT.
Statement 1: The average of j+k and k+4 is 11.
Let k=0.
Since the average of j+k and k+4 is 11, we get:
((j+0) + (0+4))/2 = 11
j = 18.
Average of j+k = (18+0)/2 = 9.
Let k=1.
Since the average of j+k and k+4 is 11, we get:
((j+1) + (1+4))/2 = 11
j = 16.
Average of j+k = (16+1)/2 = 8.5.
Since the average of j+k changes, INSUFFICIENT.
Statement 2: The average of j,k and 14 is 10.
Let k=0.
Since the average of j,k and 14 is 10, we get:
(j+0+14)/3 = 10.
j+14 = 30.
j = 16.
Average of j+k = (16+0)/2 = 8.
Let k=1.
Since the average of j,k and 14 is 10, we get:
(j+1+14)/3 = 10.
j+15 = 30.
j = 15.
Average of j+k = (15+1)/2 = 8.
Since the average of j+k stays the same, SUFFICIENT.
The correct answer is B.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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romitvsingh
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But the ans to the problem is D IN GMAT OG 11th edition pg no 308 que no 68
GMATGuruNY wrote:For those who would struggle with the algebra, an alternate approach is to plug in values.romitvsingh wrote:What is the average (arithmetic mean ) of j and k?
1) the average of j+k and k+4 is 11
2) the average of j,k and 14 is 10
Try two cases.
If the average of j+k is the same in each case, the statement is SUFFICIENT.
If the average of j+k changes, the statement is INSUFFICIENT.
Statement 1: The average of j+k and k+4 is 11.
Let k=0.
Since the average of j+k and k+4 is 11, we get:
((j+0) + (0+4))/2 = 11
j = 18.
Average of j+k = (18+0)/2 = 9.
Let k=1.
Since the average of j+k and k+4 is 11, we get:
((j+1) + (1+4))/2 = 11
j = 16.
Average of j+k = (16+1)/2 = 8.5.
Since the average of j+k changes, INSUFFICIENT.
Statement 2: The average of j,k and 14 is 10.
Let k=0.
Since the average of j,k and 14 is 10, we get:
(j+0+14)/3 = 10.
j+14 = 30.
j = 16.
Average of j+k = (16+0)/2 = 8.
Let k=1.
Since the average of j,k and 14 is 10, we get:
(j+1+14)/3 = 10.
j+15 = 30.
j = 15.
Average of j+k = (15+1)/2 = 8.
Since the average of j+k stays the same, SUFFICIENT.
The correct answer is B.
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