Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 62)
62.
(51 + 52 + 53 + ... + 100) = ?
Answer: Option
Explanation:
Sn = (1 + 2 + 3 + ... + 50 + 51 + 52 + ... + 100) - (1 + 2 + 3 + ... + 50)
| = | 100 | x (1 + 100) - | 50 | x (1 + 50) |
| 2 | 2 |
= (50 x 101) - (25 x 51)
= (5050 - 1275)
= 3775.
Discussion:
18 comments Page 2 of 2.
Khemsingh gurjar jaisingh said:
7 years ago
Solved 50/2(51+100).
=25*151,
=3775 [n/2=50/2=25.
=25*151,
=3775 [n/2=50/2=25.
(2)
DR. Roshan said:
9 years ago
Very easy way guys.
Total numbers = 50.
Middle number from 51 - 100 = 75.5.
Just multiply the middle number with 50.
i.e. 75.5 * 50 = 3775.
Total numbers = 50.
Middle number from 51 - 100 = 75.5.
Just multiply the middle number with 50.
i.e. 75.5 * 50 = 3775.
(4)
Khushi said:
1 decade ago
You guys also can do that.
a=51, n=50, d=1 so,
sn=n/2[2a+ (n-1) d].
= 50/2[2*51+(50-1)*1].
= 25[102+49].
= 25*151.
= 3775.
a=51, n=50, d=1 so,
sn=n/2[2a+ (n-1) d].
= 50/2[2*51+(50-1)*1].
= 25[102+49].
= 25*151.
= 3775.
(1)
Ankita Thakur said:
1 decade ago
The formula for sum of series = n/2[first number + last number].
Now we have to find n= [(last number - first number) / common difference]+1.
= [(100 - 51)/1] + 1.
= 50.
Therefore as @Pooja said sum of series = 50/2[50+100].
= 151*25.
= 3775.
Now we have to find n= [(last number - first number) / common difference]+1.
= [(100 - 51)/1] + 1.
= 50.
Therefore as @Pooja said sum of series = 50/2[50+100].
= 151*25.
= 3775.
(1)
Pooja said:
1 decade ago
n/2[firstnum + lastnum].
n = 50{totalnum}.
50/2[50+100].
= 25[151].
= 3775.
n = 50{totalnum}.
50/2[50+100].
= 25[151].
= 3775.
Rajkin hossain said:
1 decade ago
Look my friends
51+100=151
52+99=151
53+97=151
If we are following in that way then we have 25 times 151
So the ans is 25*151=3775.
51+100=151
52+99=151
53+97=151
If we are following in that way then we have 25 times 151
So the ans is 25*151=3775.
Tanya Mazumdar said:
1 decade ago
Thanks for the right and easiest technique.
Rupam Bhattacharjee said:
1 decade ago
You guys also can do that.........
51+52+53+.......+100
50/2(51+100)
=25*151
=3775 rule is n/2(first term+last term)=sum
51+52+53+.......+100
50/2(51+100)
=25*151
=3775 rule is n/2(first term+last term)=sum
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