NTA Abhyas JEE Main2020MathematicsPermutation and CombinationPractice
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. If the work day lasts 13 hours and to dial one combination of digits takes 5 seconds, then number of days sufficient enough to open the safe, are
Options
- A9
- B10
- C11
- D12
Correct answer
C. 11
Step-by-step solution
Total time required=(total number of dials required to sure open the lock) × 5 s = 10 5 × 5 s = 500000 60 × 60 × 13 d a y s = 10.7   d a y s Hence, 11 days are enough to open the safe.