The total number of ways in which six “+” and four ”-“ signs be arranged so that no two “-“ signs occur together is ?
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Hint: It equivalent to put 4 "-" into 7 spaces (5 between any two "+" and 2 in the head and tail). – Asydot Sep 26 '15 at 16:07
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Start by writing the $+$ signs, leaving a space between each. Since you don't want adjacent $-$ signs, then we can put at most $1$ minus sign in each available spot. There are $7$ available spots. What can you conclude?
Cameron Buie
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Excellent! If the $+$ signs are identical, there is really only one distinguishable way that we can arrange them. How then would you adjust the answer? – Cameron Buie Sep 26 '15 at 17:44
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It is worth noting that your original answer is correct, if we don't need the arrangements to be distinguishable. – Cameron Buie Sep 26 '15 at 17:48