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The easiest way to think of it is like so:
1 + 2 + 3 + .... + 18 + 19 + 20
= (1 + 20) + (2 + 19) + (3 + 18) + ... + (9 + 12) + (11 + 10)
= 21 + 21 + 21 + ... + 21 + 21 + 21
Now consider how many times that pattern will repeat. Each time we take two of those numbers and add them together, we're pulling two of them out of the sequence. That means that the total number of times we add them will always be half the length of the sequence. In this case, the length of the sequence is 20, so we'll be adding them together 10 times. In other words, the sum of the sequence will be:
(21 * 20) / 2
= 210
More generically, the sum of the numbers in an integer sequence from 1 up to any value (call it x), will be:
(x + 1)(x / 2), or (x2 + x)/2
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∙ 14y ago
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How is 20 plus 20 plus 20 equal to 1?
this is clearly a trick question. 20 plus 20 plus 20 is equal to 60 and there is 60 minites in 1 whole hour so 20 plus 20 plus 20 is equal to 1.
What is 19 plus 20 plus 1 plus 21 plus 18 plus 4 plus 25 plus 1?
109 you can plus like this: (19+1)+20+20+(1+1+18)+4+25
20 plus 1 20?
No, 20 + 1 is not 20.
1 over 4 plus 1 over 5?
so the question 1/4+1/5 find the least common denominator of the two fractions. This is 20. Now 1/4=?/20 cross multiply and you get 5. Then so 1/5= 4/20 so 4/20+5/20=9/20
If you added one tenth plus one tenth plus one twentieth plus one fourth plus one half why would you not get the answer one?
In fact, 1/10 + 1/10 + 1/20 + 1/4 + 1/2 is equal to 1.1/10= 2/20 1/4= 5/20 1/2= 10/202/20+2/20= 4/20+1/20=5/20+5/20=10/20+10/20=20/2020/20=1
How is 20 plus 20 plus 20 equal to 1?
this is clearly a trick question. 20 plus 20 plus 20 is equal to 60 and there is 60 minites in 1 whole hour so 20 plus 20 plus 20 is equal to 1.
What is 19 plus 20 plus 1 plus 21 plus 18 plus 4 plus 25 plus 1?
109 you can plus like this: (19+1)+20+20+(1+1+18)+4+25
1 plus x plus 2x equals 20then x equals?
1 + x + 2x = 20 So 1 + 3x = 20 so that 3x = 19 then x = 19/3 or 61/3
20 plus 1 20?
No, 20 + 1 is not 20.
What does 1 plus 10 plus 20 equal?
1 + 10 + 20 = 31
What is one tenth plus two twentieth?
1/10 = 2/20. So 2/20 + 2/20 = 4/20.
1 over 4 plus 1 over 5?
so the question 1/4+1/5 find the least common denominator of the two fractions. This is 20. Now 1/4=?/20 cross multiply and you get 5. Then so 1/5= 4/20 so 4/20+5/20=9/20
What does 20 plus 1 equal?
20 + 1 = 21
If you added one tenth plus one tenth plus one twentieth plus one fourth plus one half why would you not get the answer one?
In fact, 1/10 + 1/10 + 1/20 + 1/4 + 1/2 is equal to 1.1/10= 2/20 1/4= 5/20 1/2= 10/202/20+2/20= 4/20+1/20=5/20+5/20=10/20+10/20=20/2020/20=1
What plus 1 over 2 equals 7 over 20?
Suppose the answer is x.Then x + 1/2 = 7/20 so that x = 7/20 - 1/2 = 7/20 - 10/20 = -3/20
What is 10 plus 10?
The answer is 20 because if u do 0 plus 0 is 0 so 1 plus 1 is 2 so the answer is 20Twenty. 20Zwanzig. - GermanVan. - French
What is 20 plus 1?
-21
