find it in under 1 minute. show me how to do it to get picked best.=)
2006-11-01 11:02:27 · 6 answers · asked by heyy sunny. < 3 2 in Science & Mathematics ➔ Mathematics
Sum = 1 + 2 + 3 + .............. + 98 + 99 + 100
Sum = 100 + 99 + 98 + .............. + 3 + 2 + 1
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2 x Sum = 101 + 101 + 101 + .... + 101 + 101 + 101
So Sum = ½ (100 * 101)
= 5050
2006-11-01 11:32:23 · answer #1 · answered by Wal C 6 · 0⤊ 2⤋
In an arithmetic progression the sum of the terms is:
Sn = (a1 + an)*n/2
for the 1 to 100
a1 = 1
an = 100
n = 100
S100 = 101 * 100 / 2= 5050.
Now you can easily calculate for 1-1000 or 2, 4, 6, 8
.
2006-11-01 11:21:12 · answer #2 · answered by Dr. J. 6 · 0⤊ 2⤋
ok. If you take 100 + 1 you have 101. If you take 99 + 2 you have 101. this continues on. In the end you have 50 individuals sums of two numbers that equal 101. So, you take 101 and multiply it by 50 to get 5050.
2006-11-01 11:22:40 · answer #3 · answered by Brian 4 · 0⤊ 2⤋
S=n(n+1)/2 where n=100
S=50*101=5050
2006-11-01 11:05:01 · answer #4 · answered by yupchagee 7 · 1⤊ 3⤋
1 plus N quantity times N divided by 2
2006-11-01 11:07:49 · answer #5 · answered by Joe S 6 · 1⤊ 2⤋
there are 100 consecutive numbers. first and last numbers added together multiply by half of the amount
(100+1) X 100/2
101 X 50
5050
this works whenever there are an even amount of consecutive numbers
2006-11-01 11:14:27 · answer #6 · answered by Anonymous · 0⤊ 2⤋