Question:
The number of natural numbers less than 7,000 which can be formed by using the digits $0,1,3,7,9$ (repitition of digits allowed) is equal to :
Correct Option: , 2
Solution:
2 ways for $\mathrm{a}_{4}$
Number of numbers $=2 \times 5^{3}$
Required number $=5^{3}+2 \times 5^{3}-1$
$=374$