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between 10^6 and 10^7

Expert replies
by sanju09 » Tue Feb 24, 2009 4:52 am
How many different positive integers exist between 10^6 and 10^7, the sum of whose digits is equal to 2?

A. 6
B. 7
C. 5
D. 8
E. 18
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
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The Princeton Review - Manya Abroad
Lucknow-226001

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Source: — Problem Solving |

by sureshbala » Tue Feb 24, 2009 5:24 am
Clearly the number must be a 7 digit number only.

Fixing the first digit as, we can place another 1 in any of the other 6 places available. So we have 6 numbers in this case.

The other possible number is 2 followed by six 0's. (this is what most of you miss out in the exam)

Hence totally 7 numbers are possible.
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by DanaJ » Tue Feb 24, 2009 5:36 am
sureshbala wrote:Clearly the number must be a 7 digit number only.

Fixing the first digit as 1, we can place another 1 in any of the other 6 places available. So we have 6 numbers in this case.

The other possible number is 2 followed by six 0's. (this is what most of you miss out in the exam)

Hence totally 7 numbers are possible.
You missed 1.
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by sanju09 » Tue Feb 24, 2009 5:41 am
DanaJ wrote:
sureshbala wrote:Clearly the number must be a 7 digit number only.

Fixing the first digit as 1, we can place another 1 in any of the other 6 places available. So we have 6 numbers in this case.

The other possible number is 2 followed by six 0's. (this is what most of you miss out in the exam)

Hence totally 7 numbers are possible.
You missed 1.
Where, DanaJ?
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Join the discussion

by ven4gmat » Tue Feb 24, 2009 5:43 am
DanaJ wrote:
sureshbala wrote:Clearly the number must be a 7 digit number only.

Fixing the first digit as 1, we can place another 1 in any of the other 6 places available. So we have 6 numbers in this case.

The other possible number is 2 followed by six 0's. (this is what most of you miss out in the exam)

Hence totally 7 numbers are possible.
You missed 1.
I am sure he did not miss any number. We cannot have more than 7 numbers...Can you provide your logic please
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by DanaJ » Tue Feb 24, 2009 5:48 am
:))
Really funny, guys... I was saying that he missed "1" in row 2 of his explanation..... You guys thought I was talking about another number...
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by sanju09 » Tue Feb 24, 2009 5:53 am
DanaJ wrote::))
Really funny, guys... I was saying that he missed "1" in row 2 of his explanation..... You guys thought I was talking about another number...
O I C :lol:
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Join the discussion

by awesomeusername » Tue Feb 24, 2009 4:02 pm
Yup, I got 7.
1000001
1000010
1000100
1001000
1010000
1100000
2000000
Constant dripping hollows out a stone.
-Lucretius
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