Jawabanmu

2014-03-02T17:27:19+07:00
4/5 : 2 = 5/4 x 2 = 10/8
10/8 x 3 = 30/8
2014-03-02T17:32:20+07:00
Lintasan bola turun
2, 8/5, 32/25,...
a= 2, r= 4/5
Sn = a / 1-r = 2 : 1-4/5 = 10 
lintasan bola naik
8/5, 32/25, 128/125
a= 8/5 r = 4/5
Sn = 8/5 : 1-4/5 = 8
total panjang lintasan dari pantulan ke -3 = 10+ 8 = 18   :))