⎩ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎧ Row A : 1 , 2 , 3 . . . 9 Row B : 2 , 3 , 4 . . . 1 0 Row C : 3 , 4 , 5 . . . 1 1 . . . . Row I : 9 , 1 0 , 1 1 . . . 1 7 Row J : 1 0 , 1 1 , 1 2 . . . 1 8 .Find the sum of all the numbers in all the rows.
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You can look at the rows diagonally :)
The sum of all numbers of Row A to Row J is given by:
S = k = 1 ∑ 1 0 2 9 ( k + k + 8 ) = k = 1 ∑ 1 0 9 ( k + 4 ) = 9 k = 1 ∑ 1 0 k + 9 k = 1 ∑ 1 0 4 = 2 9 ( 1 0 ) ( 1 1 ) + 9 ( 1 0 ) ( 4 ) = 4 9 5 + 3 6 0 = 8 5 5
@Karthik Venkata ,good to have you back man!where were you all this time?how did you find this new problem?
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Hi, I used AP sum formula :) ! I was actually on a holiday bro .
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you mean on all the rows,individually?
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@Adarsh Kumar – All rows sum have same number of terms and common difference, and the only ones different are the first terms of the rows..
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@Venkata Karthik Bandaru – the different ones are the first and the last terms of the rows.
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@Adarsh Kumar – Hey I do not mean that, I am talking only about variables in.AP sum formula. Better let's chat on WhatsApp
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@Venkata Karthik Bandaru – oh!ok bye!
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Sum of Row A is 2 9 ( 1 + 9 ) = 4 5 .
Sum of Row B is 4 5 + 9 ( 1 ) = 5 4 , sum of Row C is 5 4 + 9 ( 1 ) = 6 3 , and so on.
The sums form an AP with a 1 = 5 4 and a 1 0 = 1 2 6 .
Hence, 2 1 0 ( 4 5 + 1 2 6 ) = 8 5 5 .