John invested a sum of money at an annual simple interest rate of 10%. At the end of four years the amount invested plus interest earned was Rs.770. The amount invested was:

Explanation:

Let the amount invested =Rs. P

According to the question,

P+P×10×4\100=770

P+4P\10=770

14P\10=770

P=770×10\14= Rs. 550

Hence, Required invested amount = Rs.550

Aternate

10%=1→Interest\10→Principal

Interest in 4 years=1×4=4

Amount=(interest+principal)

=4+10=14

According to the question,

14 units=770

1 unit=770\14

10 units=770\14×10= Rs.550

The amount invested = Rs.550