(1), (2, 3), (4, 5, 6), (7, 8, 9, 10)…..
Sum of the numbers in the 50th bracket is ___.

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Solution

The last number in the first bracket is 1 $(\sum 1)$
The last number in the second bracket is 3 $(\sum 2)$
The last number in the third bracket is 6 $(\sum 3)$
The last number in the fourth bracket is 10 $(\sum 4)$
The last number in the 49th bracket is $(\sum 49)$ = 1225
The last number in the 50th bracket is $(\sum 50)$ = 1275
Sum of the numbers in the 50th bracket = 1226 + 1227 + …...1275
$= (\frac{50}{2}) (1226 + 1275) = 62525$

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(1), (2, 3), (4, 5, 6), (7, 8, 9, 10)….. Sum of the numbers in the 50th bracket is ___.

(1), (2, 3), (4, 5, 6), (7, 8, 9, 10)…..
Sum of the numbers in the 50th bracket is ___.