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SMO 2007 Senior Round 1 Question 2

SMO · SMO 2007 Senior Round 1

Question 2

A bag contains $x$ green and $y$ red sweets. A sweet is selected at random from the bag and its colour noted. It is then replaced into the bag together with 10 additional sweets of the same colour. A second sweet is next randomly drawn. Find the probability that the second sweet is red.
  1. $\dfrac{y+10}{x+y+10}$
  2. $\dfrac y{x+y+10}$
  3. $\dfrac y{x+y}$
  4. $\dfrac x{x+y}$
  5. $\dfrac{x+y}{x+y+10}$