Probability, SM-Bank 066

A bag contains different coloured balls.

It contains 4 red balls, 8 green balls, 3 pink balls, 6 grey balls and 11 yellow balls.

Nathalie picks a ball from the bag without looking.

What is the chance that she draws a grey ball? (1 mark)
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What is the chance that the ball she draws in not pink? (2 marks)
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Show Answers Only

a. \(\dfrac{3}{16}\)

b. \(\dfrac{29}{32}\)

Show Worked Solution

a.	\(P\text{(Grey ball)}\)	\(=\dfrac{\text{Number of grey balls}}{\text{Total number of balls}}\)
		\(=\dfrac{6}{4+8+3+6+11}\)
		\(=\dfrac{6}{32}\)
		\(=\dfrac{3}{16}\)

b.	\(P\text{(not pink ball)}\)	\(=1-P\text{(pink ball)}\)
		\(=1-\dfrac{\text{Number of pink balls}}{\text{Total number of balls}}\)
		\(=1-\dfrac{3}{32}\)
		\(=\dfrac{29}{32}\)