0.658=0+6×8−1+5×8−2
= 0 + 68+564 = 0.828125 base 10
0.828125 base 10 to base 2
read answer from up to down
0.828125 in base 10 = 0.110101 in base 2.
Therefore, 0.65 in base 8 = 0.110101 in base 2.