Find number at column 2 and row 6
Q1. How to use this pattern ?
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* Top row 1 : The numbers are triangular numbers if column number is even
* Top row 1 : The number in column x is x*(x+1)/2 if column number is even
Q2. Find the number at row 4 and column 5
A2. Answer
- If top row 1 number is x*(x+1)/2
- Hence number = 1 + 2 + 3 + .... +(r + c - 2) + r
- Number = 1 + 2 + 3 + .... (4 + 5 - 2) + 5 = 28 + 5 = 33
- x*(x+1)/2 >= 33
- x = 6, x*(x+1)/2 = 21
- x = 7, x*(x+1)/2 = 28
- x = 8, x*(x+1)/2 = 36
- Since x = 8, x*(x+1)/2= 36 (triangular number)
- Hence this is the answer : Number at row 4 and column 5 is 33
Q3.
A3. Answer
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