Pens

Probability Level 2

Lucy have three red pens and three black pens in a drawer. Yesterday she picked at random a pen from the drawer and putted in her purse. Today she putted a black pen in the purse. What is the probability of Lucy take a black pen in the purse now?

3 4 \frac{3}{4} 2 3 \frac{2}{3} 1 2 \frac{1}{2} 5 6 \frac{5}{6}

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Victor Paes Plinio by Victor Paes Plinio , 21, Brazil

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2 solutions

Aaaaa Bbbbb
Sep 20, 2014

P r o b = 3 6 × 1 2 + 1 2 = 3 4 Prob=\frac{3}{6} \times \frac{1}{2}+\frac{1}{2}=\boxed{\frac{3}{4}}

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Saya Suka
Mar 24, 2021

P(black pen from purse)
= (3/6) × (1/2) + (3/6) × (2/2)
= 1/4 + 1/2
= 3/4


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