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Find the sum of numbers in the 200th box
(1) + (2 + 3) + (4 + 5 + 6) + (7 + 8 + 9 + 10) + ......................
Easy... just think a bit... not for all experts... but try...!!
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3 Answers
39
49number of numbers till 199th box=1+2+3+4+5+.....199 terms..=199x200/2=19900
so first number of 200th box is 19901
and there are 200 numbers.
so sum is 200x19900 + 200x201/2=3980000+20100= 4000100 (ans)
36Alternate
Since the first box has 1 number, 2nd has 2 numbers, 3rd has 3 clearly, 200th will have 200
Now,
Total number of terms in the series, 1,2,3,........................
=1 + 2 + 3 + .................. + 200 = 200 x 201 / 2 = 20100
Hence, last term of the 200th box = 20100
Total terms in the series excluding the 200th box = 1 + (20100 - 200 - 1)(1) = 19900
Hence, sum of all the terms including all the boxes = 202015050
sum of all the terms excluding the terms of 200th box = 198014950
Hence, sum of all the terms in the 200th box = 4000100 Ans...