## Progressive Countdown

If you’re given a number, subtract 1, then 2 from the result, then 3 from that result and so on until you reach 0 or a negative number.

For example, if you’re given 15:

15 – 1 = 14

14 – 2 = 12

12 – 3 = 9

9 – 4 = 5

5 – 5 = 0

Which of these numbers will finish exactly at zero?

102 103 104 105 106

105

105 – 1 = 104

104 – 2 = 102

102 – 3 = 99

99 – 4 = 95

95 – 5 = 90

90 – 6 = 84

84 – 7 = 77

77 – 8 = 69

69 – 9 = 60

60 – 10 = 50

50 – 11 = 39

39 – 12 = 27

27 – 13 = 14

14 – 14 = 0

Posted in Brain Teasers

2 Comments on "Progressive Countdown"? says

April 29, 2017 @ 03:41

I got this one right- who else????

Vishal Garg says

May 1, 2017 @ 01:49

There is a logic behind solving this problem.

You have to check the sum of 1 to n numbers by formulla,

sum = n*(n+1)/2

Now start putting n from 1 and you will get your answer.

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