Question

There are 5 blue pens (B1, B2, B3, B4, and B5), and 4 red pens (R1, R2, R3, and R4) in the drawer. Mark picks one blue and one red pen from a drawer and uses it. What is the probability of Mark taking a blue B1 pen and any red pen? (Assume that drawing pens from the drawer is equally likely.)

• A. $\frac{1}{3}$
• B. $\frac{1}{4}$
• C. $\frac{1}{5}$
• D. $\frac{1}{20}$

Answer 1

The correct option is C $\frac{1}{5}$

Number of red pens $=4$
Number of blue pens $=5$
Total number of possible outcomes from the table $=5\times 4=20$

R1- B1	R2- B1	R3- B1	R4- B1
R1- B2	R2- B2	R3- B2	R4- B2
R1- B3	R2- B3	R3- B3	R4- B3
R1- B4	R2- B4	R3- B4	R4- B4
R1- B5	R2- B5	R3- B5	R4- B5

Number of ways Mark picks a blue B1 pen and any red pen $=4$
Hence, the probability of Mark picking a blue B1 pen and any red pen $=\frac{\text{Number of ways Marks picks a blue B1 pen and any red pen}}{\text{Total number of possible ways of picking two pens}}=\frac{4}{20}=\frac{1}{5}$