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Number System

by harsh.champ » Tue Feb 09, 2010 5:06 am
The digit 1 is attached to the right of a 3-digit number making it a 4-digit number which is 7777 more than the given number. The sum of the digits of the number is

(A)23
(B)18
(C)17
(D)16
(E)21

The OA is B.
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by shashank.ism » Tue Feb 09, 2010 5:14 am
harsh.champ wrote:The digit 1 is attached to the right of a 3-digit number making it a 4-digit number which is 7777 more than the given number. The sum of the digits of the number is

(A)23
(B)18
(C)17
(D)16
(E)21

The OA is B.
Let the 3-digits of the given number be a, b and c, so that abc1 may be the 4 digit number. The difference between the numbers is (1000a + 100b + 10c + 1) - (100a + 10b + c) = 7777

--> 9 (100a + 10b + c) = 7776
--> 100a + 10b + c = 864 (which is the given number)

So, the sum of the digits of the given number is 18.[spoiler]The answer is option (B)[/spoiler]
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by ajith » Tue Feb 09, 2010 6:41 am
harsh.champ wrote:The digit 1 is attached to the right of a 3-digit number making it a 4-digit number which is 7777 more than the given number. The sum of the digits of the number is

(A)23
(B)18
(C)17
(D)16
(E)21

The OA is B.
say abc be the number

100a + 10b +c +7777 = 1000a + 100b + 10c + a
7777 = 900a + 90 b +9 c +1
= 9 (100a+10b+c) =1
(100a+10b+c) = 7776/9 =864
sum of digits = 16
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by shashank.ism » Tue Feb 09, 2010 10:19 am
ajith wrote:
harsh.champ wrote:The digit 1 is attached to the right of a 3-digit number making it a 4-digit number which is 7777 more than the given number. The sum of the digits of the number is

(A)23
(B)18
(C)17
(D)16
(E)21

The OA is B.
say abc be the number

100a + 10b +c +7777 = 1000a + 100b + 10c + a
7777 = 900a + 90 b +9 c +1
= 9 (100a+10b+c) =1
(100a+10b+c) = 7776/9 =864
sum of digits = 16
ajit you did a calculation mistake sum of digits of 864 = 8+6+4 =18
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by vinay_mashetty » Fri Jul 15, 2011 5:40 am
- - - 1
(-)x
........
7 7 7 7

1-x i.e, 11-x = 7. So, x=4

- - 4 1
(-)y 4
........
7 7 7 7

4-y i.e, 13-y=7. So, y=6

- 6 4 1
(-)z 6 4
.......
7 7 7 7

6-z i.e, 15-z=7.So, z=8

8 6 4 1
(-)8 6 4
.......
7 7 7 7
.......
Sum of the digits of the number is 8+6+4 =18 .
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