0.3
Change the divisor 3.78 to a whole number by moving the decimal point 2 places to the right. Then move the decimal point in the dividend the same, 2 places to the right.
We then have the equations:
1260 ÷ 378 = 3.333
and therefore:
12.6 ÷ 3.78 = 3.333
Both calculated to 3 decimal places.