Q. The lock of a safe consists of five discs each of which features the digits 0, 1, 2, … ,9.The safe can be opened by dialing a special combination of the digits. The number of days sufficient enough to open the safe. If the work day lasts 13 h and 5 s are needed to dial one combination of digits is
A) 9
B) 10
C) 11
D) 12
Explanation
(c)
Total time required=(total number of dials required to sure open the lock)$\times 5s$
$= 10^{5} \times 5s$
$= \frac{500000}{60 \times 60 \times 13}days = 10.7\ days$
Hence, 11 days are enough to open the safe.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.