Number 21 would be 6 39/40
Given:
Principal = ₹ 5000
Compound rate of interest = 6% per annum
Time = 3 years
To find:
The amount after 3 years of compound interest.
Solution:
Formula for amount is:

Where, P is principal, r is rate of interest in % and t is the number of years.
Putting P=5000, r=6 and t=3, we get



On further simplification, we get



Therefore, the amount after 3 years of compound interest is 5955.08.
83 and 89 are prime numbers between 80 and 90.
8/10= 4/5
4/5 is the simplest form (: