CareerCup

For 1.5 years,
Use 2 tyres for 6 months. then change one of the tyre and use new one, it will work again 6 months. then, First one get expired so replace that with first replace tyre. this will last again 6 months.

so total 6+6+6 months = 1.5 months

We can use them for 1.5 years.
First use two tyres for 4 months, After that change one.
Then again after 4 months change the older one with one already used for 4 months. And like this using on rotaion we can use them for 18 months.. :)

yes the correct answer is 18 months ie 1.5 years .. we have 3 tyres and we have to maximize the duration of usage of Scooter so.. Its better that we shld use each of the tyre equally so that cumulative sum of periods is max and we use all tyre upto their max life

Yes, 1.5 years is correct assuming what everyone else assumes.

However, how many wheels does this scooter have? Max life on what terrain? Is every terrain the same wear?

1.5 years if a one time 2 tyres are used by the scooter..
1 year if the scooter was a tricyclic.

use each for 3 month with combination so that total time is 18 month.

use the first two for half year. Both will be half worn.
Then use the one half with the third one and the other half with the third. So 1.5 years

there are 3 tires;
total life period=3*1=3years
if scooter has two tires=3/2=1.5years