In how many years will Rs. 2000 may becomes Rs. 2420 at the rate of 10% compound interest per annum.

2

          Principal      :      Amount

            2000         :       2420

             100          :         121  ......(i)

Now,

10% = \(\frac{1}{10}\)

Therefore,

                        Principal      :      Amount

in 1 year:              10           :         11

in 2 year:             10²         :         11²

                            100         :        121   .....(as given in (i))

Hence the time is 2 years.