You are given a new car. All the four tyres are new. Also there is a new spare tyre inside the car. You have to travel one thousand kilometers , but each tyre will wear out and become useless after running eight hundred kilometers . You can make use of all the five tyres and change them at your discretion ( among the given five tyres only ). Please give the solution under spoiler.
Spoiler: Answer Let the car travel for 200KM. Now change first tyre with new tyre and travel 200KM more T1 - 200km, T2- 200km, T3-200km, T4 - 200km, spare - 0Km Now replace 1st tyre as it is and change 2nd tyre with new tyre and travel 200KM more T1 - 200km, T2- 200km, T3-400km, T4 - 400km, spare - 200Km Now replace 2nd tyre as it is and change 3rd tyre with new tyre and travel 200KM more T1 - 400km, T2- 400km, T3-400km, T4 - 600km, spare - 400Km Now replace 3rd tyre as it is and change 4th tyre with new tyre and travel 200KM more T1 - 600km, T2- 600km, T3-600km, T4 - 800km, spare - 600Km you'll reach your destination
Need to change one tyre every after 200 kms.... Tyre 1, Tyre 2, Tyre 3, Tyre 4 & Tyre 5: Replace the 1st tyre with spare 5th tyre after 200 kms and keep the 1st tyre in the car.....replace the 2nd tyre after 400kms with the spare tyre (1st tyre) lying in the car and keep the 2nd tyre in the car, after 600 kms replace 3rd tyre and finally the 4th tyre after 800 kms.....every time we have a spare tyre in the car with some left over kms till we finish the journey.....