Explanation:
multiplying by a power of 10 (e.g. 10¹=10, 10² = 100, 10³=1000, ...) moves the decimal point the same number of positions to the right as the exponent of 10.
if there are no more digits, then 0s are added to the right.
e.g.
5743 × 1000 = 5743000
78.3954 × 1000 = 78395.4
dividing by a power of 10 moves the decimal point the same number of positions to the left as the exponent of 10.
if there are no more digits, then 0s are added to the left (one 0 to the left of the decimal point to make it a complete number, the other actually needed 0s to the right of the decimal point).
e.g.
5743 / 1000 = 5.743
78.3954 / 1000 = 0.0783954
so, in our cases here
1.
123 / 100 = 1.23
2.
3 / 10 = 0.3