If $64 amount to $ 83.20 in 2 years. what will $ 86 amount to in 4 years at the same rate percent per annum?  Choose the correct option
A) $127.40
B) $124.70
C) $114.80
D) $137.60
E) $117.40
First, Simple interest formula is   S.I=PNR/100 Here P=$64, T=2 years and S.I=$19.20 (i.e 83.20-64)   R=((100x19.20)/(64x2))%=15%   Now P=$86, T=4 years, R=15%   so S.I=86x4x15/100=$137.60   Answer is $137.60
<result>D</result>
If $64 amount to $ 83.20 in 2 years. what will $ 86 amount to in 4 years at the same rate percent per annum?