Instruct your students to solve the equation as though there were no decimal points. Once they have the answer, teach them to count the number of numerals to the right of each decimal point, then count in that number of digits from the right of the answer and insert the decimal point here. For instance, when figuring 10.5 times 10.5, they would remove the decimals and multiply 105 and 105, with the answer of 11,025. Since there are two numbers to the right of decimal points, the answer is 110.25.
Teach your students that when they are multiplying a whole number by a decimal, they can replace the word "times" by the word "of." For instance, if they are multiplying 10 times 0.5, they are actually figuring out the answer to 0.5, or half, of 10. When they do the actual multiplication, have them remove the decimal, so that their answer in this case is 50, then move the decimal point by the number of numerals to the right of the decimal. In the example, they will come up with the answer 5, or half of 10.
Show students that multiplying a whole number by a multiple of 10 simply moves the decimal point to the right. For instance, in 5 times 10 to the fifth power, move the decimal five places to the right, with the resulting sum of 500,000.