Question

Seven chits are numbered 1 to 7. Three are drawn one by one with replacement. The probability that the least number on any selected chit is 5, is

• A. $1 - \left( \frac { 2 } { 7 } \right) ^ { 4 }$
• B. $4 \left( \frac { 2 } { 7 } \right) ^ { 4 }$
• C. $\left( \frac { 3 } { 7 } \right) ^ { 3 }$
• D. None of these

Answer 1

Answer: (C)

$\left( \frac { 3 } { 7 } \right) ^ { 3 }$

Answer 2

$P ( 5$ or 6 or $7 )$ in one draw $= \frac { 3 } { 7 }$

$\therefore$ Probability that in each of 3 draws, the chits bear 5 or 6 or