In a box, there is 1 more green pens than black pens. The probability of taking 2 black pens is 0.2 . How many pens are in the box?
g = b+8g+b = p = 2b+1(b/p) x (b-1)/(p-1) = 1/5(b^2 - b)/(p^2 - p) = 1/5sub in p= 2b+1(b^2 - b)/(4b^2 + 2b) = 1/55b^2 - 5b = 4b^2 + 2bb^2 -7b = 0b = 7 or b = 0 (cannot be 0 as 2 pens must be taken)p = 2(7) + 1 = 15 pens
JL
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