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A bag contains x counters. 7 of the counters are blue. Sam takes at random a counter from the bag and does not replace it. Jill then takes a counter from the bag. The probability they both take a blue counter is 0.2. Form an equation involving x, in the form x + bx +c=0.

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Answer:

0.2x² - 0.2x - 42 = 0

Step-by-step explanation:

Number of counters = x

Number of blue counters =7

Probability, p = required outcome / Total possible outcomes

P(Sam picks blue ) : = 7/x

P(jill picks blue) = 6/(x - 1)

P(Sam picks blue) * P(Jill picks blue) = 0.2

7/x * 6/(x-1) = 0.2

42/x(x - 1) = 0.2

42 / x² - x= 0.2

42 = 0.2(x² - x)

42 = 0.2x² - 0.2x

0.2x² - 0.2x - 42

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