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by ajith » Wed Apr 14, 2010 2:49 am
eaakbari wrote:1122334444...
In above sequence, what is the 100th digit

A 1
B 2
C 3
D 4
E 5
There is nothing to confirm a pattern here.... Are you sure about the question
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by eaakbari » Wed Apr 14, 2010 3:01 am
Its from a GRE Prep Material, but the question holds good. I have the OA and I did solve in some way but want to see better methods
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by neoreaves » Wed Apr 14, 2010 3:06 am
is the question in this pattern

1223334444...


There are two 2's ...three 3's ...four 4's .....
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by eaakbari » Wed Apr 14, 2010 3:09 am
neoreaves wrote:is the question in this pattern

1223334444...


There are two 2's ...three 3's ...four 4's .....
Yeah
122333444455555666666...
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by eaakbari » Wed Apr 14, 2010 3:19 am
If we want to find the 100th digit,
We can observe this forms an A.P 1+2+3+4.....
Which is the number of digits

Hence for Sum = 100

100 = n(n+1)/2

Choose n to be a whole number for easier calculation which is closer to 100. We can take n = 14

So when n = 14, term will be 105. So 104 and 105 will be the last numbers with 14 . That means

1 4 1 4 1 4
100 101 102 103 104 105

Therefore Answer is 1

But to come to this conclusion I took a lot of time. Experts please comment on this
Hence answer = A

OA = A

I do not have OE
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by kstv » Wed Apr 14, 2010 4:34 am
The 45th digit is the last single digit.
1+2+3...........9=45

After that all the even no digit till 190th digit are 1
cos after 9 (45th) it is 10
46th to digit 1 and 47th digit is 0
48th digit 1 49th digit 0

100th is an even no digit so it will be 1.
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by neoreaves » Wed Apr 14, 2010 4:52 am
The pattern can be mapped to Arithmetic series sum which relates to the digits position

So,
Using Arithmetic series sum formula

for 1-9 the sum comes out to be 9/2(1+9) = 45

Thus 45th digit is 9 and 46th onwards are two-digit numbers starting from 10

Now we need to find 100th digit ...so 100 - 45 = 55 ...since after 45 we have double digits so we divided 55/2 = 27.5 ...thus we need to find the first digit of the two-digit number ...which in this case is 1


Thus A
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by thephoenix » Wed Apr 14, 2010 5:04 am
IMO A
45th digit is 9(last of 9 series)
since 46th digit is one and here onwards the even digit is one till 19 series
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by pradeepkaushal9518 » Wed Apr 14, 2010 6:04 am
1223334444....97 th will be 3 (13 ) then 141414

98th 1
99th 4
100th 1
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