Math Is Fun Forum
Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °
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#1 2008-11-01 07:46:30
- tony123
- Member
- Registered: 2007-08-03
- Posts: 230
how many
It is possible to replace each of the ± signs below by either – or + so that
± 1 ± 2 ± 3 ± 4 ± ... ± 96 = 1996.
At most how many of the ± signs can be replaced by a + sign?
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#2 2008-11-01 08:06:44
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: how many
1+2+3+4+5+...+76 - 77 + 78+...+82 - 83 - 84 - ... - 95 - 96 = 1996.
ie. there are + signs before the numbers from 1 to 82 inclusive, except for 77.
This means that the maximum number of + signs in the equation is 81.
Why did the vector cross the road?
It wanted to be normal.
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