Jawabanmu

2014-08-07T23:31:55+07:00
Bayangan  : 15x21cm
asli  : 25x?m
25m = 2500cm

2500/15 = x/21 (x=lebar asli)
2500/5 = x/7
500 = x/7
3500 = x
lebar asli = 35m

atau

15/21 = 2500/x
5/7 = 2500 / x
5x = 17500
x = 3500
x = 35m
2014-08-07T23:35:35+07:00
15cm/21cm = 2500cm/L
15cmxL = 2500cmx21cm
15cmxL = 52500cm
L = 52500cm/15cm
L = 3500cm
L= 35m