When Xiao Ming was doing math, he forgot to write decimal points when writing numbers. The result is 40.5 more than the correct number, and the correct number is 4.5. Xiao Ming wrote 45, so there was 45-4.5=40.5.

The law of fractional division in which divisor is decimal;

1) First look at how many decimal places the divisor has, and then move the decimal point of the divisor by a few places to the right. If it is not enough, use zero to make up the digits.

2) Then divide by the fractional division of integer divisor.

Law of fractional division:

1) The numerator of the dividend is multiplied by the denominator of the divisor as the numerator.

2) The denominator of the dividend is multiplied by the numerator of the divisor as the denominator. (that is, the dividend is a constant, which is the reciprocal of multiplication and division)