Q)Santa estimates that 10% of the children in the world have been good this year but do not celebrate Christmas, and that 50% of the children who celebrateChristmas have been good this year. If 40% of the children in theworld have been good, what percentage of children in the world are notgood and do not celebrate Christmas?
How can i do such a problem in less than 2 mins.i hate reading such a long question as it really has bad effect on my speed and flow.need help on this!!
Word problem - II
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Say, there are 100 children in the world.'manpreet singh wrote:Q)Santa estimates that 10% of the children in the world have been good this year but do not celebrate Christmas, and that 50% of the children who celebrate Christmas have been good this year. If 40% of the children in the world have been good, what percentage of children in the world are not good and do not celebrate Christmas?
Hence, 10 children are good but do not celebrate Christmas.
And 40 children are good.
--> (40 - 10) = 30 children are good and celebrate Christmas.
--> 30 = 50% of number of children who celebrate Christmas.
--> 60 children celebrate Christmas.
--> 40 children do not celebrate Christmas.
Hence, (40 - 10) = 30 children are not good and do not celebrate Christmas.
Therefore, required percentage = 30%
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Anurag Sir,
I have a doubt on this question, basically the data that you have taken.
Let us say, x= no. of children who are good and do not celebrate Christmas.
y= no. of children who are good and celebrate Christmas.
z= no. of children who celebrate Christmas and are not good.
and w= no. of children who are not good and do not celebrate christmas.
Now, as per the question,
x = 10
x + y = 40, => hence y = 30
the question says," 50% of the children who celebrate Christmas have been good this year"
So, 50 % of (y + z) = (x + y), => hence z = 50.
Going by this I get w = 100 - (x + y + z) = 10, meaning 10% of children are not good and do not celebrate christmas.
Please tell me the blunder that i just cannot see.
I have a doubt on this question, basically the data that you have taken.
Let us say, x= no. of children who are good and do not celebrate Christmas.
y= no. of children who are good and celebrate Christmas.
z= no. of children who celebrate Christmas and are not good.
and w= no. of children who are not good and do not celebrate christmas.
Now, as per the question,
x = 10
x + y = 40, => hence y = 30
the question says," 50% of the children who celebrate Christmas have been good this year"
So, 50 % of (y + z) = (x + y), => hence z = 50.
Going by this I get w = 100 - (x + y + z) = 10, meaning 10% of children are not good and do not celebrate christmas.
Please tell me the blunder that i just cannot see.
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x children do not celebrate Christmas. Hence, they cannot be part of this equation. It should be 50% of (y + z) = y ---> z = y = 30myselfhari wrote:the question says," 50% of the children who celebrate Christmas have been good this year"
So, 50 % of (y + z) = (x + y), => hence z = 50.
Therefore, w = 100 = (x + y + z) = 100 - (10 + 30 + 30) = 100 - 70 = 30
Hope that helps.
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This is an EITHER/OR group question.'manpreet singh wrote:Q)Santa estimates that 10% of the children in the world have been good this year but do not celebrate Christmas, and that 50% of the children who celebrateChristmas have been good this year. If 40% of the children in theworld have been good, what percentage of children in the world are notgood and do not celebrate Christmas?
How can i do such a problem in less than 2 mins.i hate reading such a long question as it really has bad effect on my speed and flow.need help on this!!
Every child is EITHER good OR not good.
Every child EITHER celebrates Christmas OR does not.
For an EITHER/OR group problem, use a GROUP GRID to organize the data.
Let G = good, NG = not good, C = celebrates, DC = doesn't celebrate.
Here's the grid, with 100 children plugged in for the total.
Now let's use the information in the problem to complete the grid step by step._______________G______NG_______Total
C:
DC:
total:___________________________100
As soon as we know 2 entries in a row or a column, we can calculate the remaining entry in that row or column.
10% of the children in the world have been good this year but do not celebrate Christmas:
50% of the children who celebrate Christmas have been good this year._______________G______NG_______Total
C:
DC:____________10
total:____________________________100
Since we don't yet know how many celebrate Christmas, hold onto this information.
40% of the children in the world have been good:
Now let's return to the information we skipped over:_______________G______NG_______Total
C:_____________30
DC:____________10
total:___________40______60_______100
50% of the children who celebrate Christmas have been good this year.
Since 30 children who celebrate Christmas have been good, the total number who celebrate Christmas = 60:
Now we can answer the question:_______________G______NG________Total
C:_____________30______30_________60
DC:____________10______30_________40
total:___________40______60________100
Not good and do not celebrate = 30.
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Hi Mitch,
As soon as I saw this question, I approached it with the same logic that you have mentioned but it still took me about 4 mins to solve. I think it's because I have encountered and solved a very few questions of similar type before. Can you please post a link where I can find 5-6 similar questions.
Thanks.
Niket
As soon as I saw this question, I approached it with the same logic that you have mentioned but it still took me about 4 mins to solve. I think it's because I have encountered and solved a very few questions of similar type before. Can you please post a link where I can find 5-6 similar questions.
Thanks.
Niket
GMATGuruNY wrote:This is an EITHER/OR group question.'manpreet singh wrote:Q)Santa estimates that 10% of the children in the world have been good this year but do not celebrate Christmas, and that 50% of the children who celebrateChristmas have been good this year. If 40% of the children in theworld have been good, what percentage of children in the world are notgood and do not celebrate Christmas?
How can i do such a problem in less than 2 mins.i hate reading such a long question as it really has bad effect on my speed and flow.need help on this!!
Every child is EITHER good OR not good.
Every child EITHER celebrates Christmas OR does not.
For an EITHER/OR group problem, use a GROUP GRID to organize the data.
Let G = good, NG = not good, C = celebrates, DC = doesn't celebrate.
Here's the grid, with 100 children plugged in for the total.
Now let's use the information in the problem to complete the grid step by step._______________G______NG_______Total
C:
DC:
total:___________________________100
As soon as we know 2 entries in a row or a column, we can calculate the remaining entry in that row or column.
10% of the children in the world have been good this year but do not celebrate Christmas:50% of the children who celebrate Christmas have been good this year._______________G______NG_______Total
C:
DC:____________10
total:____________________________100
Since we don't yet know how many celebrate Christmas, hold onto this information.
40% of the children in the world have been good:Now let's return to the information we skipped over:_______________G______NG_______Total
C:_____________30
DC:____________10
total:___________40______60_______100
50% of the children who celebrate Christmas have been good this year.
Since 30 children who celebrate Christmas have been good, the total number who celebrate Christmas = 60:
Now we can answer the question:_______________G______NG________Total
C:_____________30______30_________60
DC:____________10______30_________40
total:___________40______60________100
Not good and do not celebrate = 30.
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Here you go:niketdoshi123 wrote:Hi Mitch,
As soon as I saw this question, I approached it with the same logic that you have mentioned but it still took me about 4 mins to solve. I think it's because I have encountered and solved a very few questions of similar type before. Can you please post a link where I can find 5-6 similar questions.
Thanks.
Niket
https://www.beatthegmat.com/applicants-t84647.html
https://www.beatthegmat.com/gmat-test-takers-t88286.html
https://www.beatthegmat.com/avoiding-alg ... 05954.html
https://www.beatthegmat.com/650-800-question-t68610.html
https://www.beatthegmat.com/interns-at-h ... 62065.html
https://www.beatthegmat.com/problem-solving-t84791.html
https://www.beatthegmat.com/probability- ... 66390.html
https://www.beatthegmat.com/700-ds-tough ... 57-15.html
https://www.beatthegmat.com/please-help- ... 86596.html
If you type "group grid" into the search bar, you might find more.
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For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
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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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Hi Mitch its a fast method you used here, just saw that in Manhattan book also , but i think we need to read the problem carefully as there is tricky statement(50% of the children who celebrate Christmas have been good this year)...
What i did wrong trying to solve this problem fast was putting 50 in good children and Christmas celebrating
_______________G______NG_______Total
C:_____________50
DC:____________10
total:___________40______60_______100
which was a blunder!!!but tempting thing to do since i was solving it fast...
so one need to understand the statement carefully before going ahead with solution.
What i did wrong trying to solve this problem fast was putting 50 in good children and Christmas celebrating
_______________G______NG_______Total
C:_____________50
DC:____________10
total:___________40______60_______100
which was a blunder!!!but tempting thing to do since i was solving it fast...
so one need to understand the statement carefully before going ahead with solution.