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sum of the first

by sanju09 » Thu May 06, 2010 5:00 am
The sum of the first 100 positive integers is 5,050. What is the sum of the first 200 positive integers?
(A) 10,100
(B) 10,200
(C) 12,400
(D) 15,050
(E) 20,100
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by ajith » Thu May 06, 2010 5:03 am
sanju09 wrote:The sum of the first 100 positive integers is 5,050. What is the sum of the first 200 positive integers?
(A) 10,100
(B) 10,200
(C) 12,400
(D) 15,050
(E) 20,100
[spoiler]
Sum of first 100 positive integers = 5050
Sum of next 100 positive integers = 100*100 + 5050 = 15050

Sum of first 200 positive integers = 5050+15050 = 20100[/spoiler]
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by liferocks » Thu May 06, 2010 6:32 am
sum of the first 200 positive integers
=sum of the first 100 positive integers + 100*100+sum of the first 100 positive integers
=5050*2+10000
=10100+10000
=20100

Ans option E
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by clock60 » Thu May 06, 2010 11:09 am
did not get for what purpose we are given the sum of first 100 integers
it is simple AP with 1 st =1 and 200th=200, find the sum of first 200
S(200)=(1+200)/2*200=20100
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by harshavardhanc » Thu May 06, 2010 12:24 pm
clock60 wrote:did not get for what purpose we are given the sum of first 100 integers
it is simple AP with 1 st =1 and 200th=200, find the sum of first 200
S(200)=(1+200)/2*200=20100
precisely! our objective is to find the sum of first 200 integers. Answer wouldn't change whether you use the information provided in the question or not :) . Sum of AP will work fine!
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by kstv » Thu May 06, 2010 11:06 pm
If I modify the Q

Sum of 100 consecutive intergers = x
what is the sum of the next 100 consecutive integers.
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by harshavardhanc » Thu May 06, 2010 11:42 pm
kstv wrote:If I modify the Q

Sum of 100 consecutive intergers = x
what is the sum of the next 100 consecutive integers.
it will be x + 100^2. let me know if you need the explanation ;)
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