Answer:
4.50 yr
Explanation:
I assume that this is compound interest. 
The compound interest equation is 

You don't give the frequency of compounding, so I assume that it is once per year. 
Data: 
A = ₹117 000 
P = ₹90 000 
r = 6 % = 0.06 
n = 1 
 
Calculations: 


 
Divide each side by 90 0000 

 
Take the logarithm of each side 
log1.3 = tlog1.06 
0.1139 = 0.025 31t 
 
Divide each side by 0.025 31 
t = 4.50 yr 
You can buy your magic carpet in 4.50 yr.