The number of 3-digit numbers, formed using the digits $2,3,4,5$ and 7 , when the repetition of digits is…
The number of 3-digit numbers, formed using the digits $2,3,4,5$ and 7 , when the repetition of digits is not allowed, and which are not divisible by 3 , is equal to__________
Solution
total number of three digit numbers not divisible by 3 will be formed by using the digits
$\begin{aligned}
& (4,5,7) \\
& (3,4,7) \\
& (2,5,7) \\
& (2,4,7) \\
& (2,4,5) \\
& (2,3,5) \\
& \text { number of ways }=6 \times 3 !=36
\end{aligned}$