Student: I remember that a decimal is a number that is less than one!

Mentor: That's right, but -1 is less than one. Is it a decimal?

Student: No, so a decimal is between 0 and 1.

Mentor: That's very good. Can anyone think of an example of this?

Student: Twenty-five hundredths, which is written as 0.25 or .25 is a decimal.

Mentor: Great example! Now does anyone remember what a mixed number is?

Student: I think it is a number that has both a whole number and a decimal in it. Like one and five tenths, written 1.5.

Mentor: You know this well!

Mentor: Now do you recall how to multiply decimals?

Student: It's like multiplying regular numbers only you have to add the decimal point when you're done.

Mentor: Good, do you remember how to determine where the decimal goes?

Student: I think that you count all the decimal places on the numbers that you multiplied together and that's how many places are in the answer.

Mentor: Right. So if I multiplied 0.25 by 0.1, how many decimal places would the final answer have?

Student: Three!

Mentor: Okay, so what is that result?

Student: Um, hang on... it's .025?

Mentor: Good. Now who can tell me how to multiply mixed numbers?

Student: Its the same as multiplying with decimals, you count the number of decimal places in the original problem and that is how many there are in the answer.

Mentor: That's correct too but you do need to be careful not to count trailing zeros. For instance, if you have 1.25 multiplied by 1.50 how many decimal places should be in your final answer?

Student There would only be three because the number 1.50 has a trailing zero so that shouldn't be counted as a decimal place. So the final answer is 1.875.

Mentor: Exactly. What about multiplying 1.25 by 1.05?

Student: There would be four decimal places because the 0 in 1.05 is not a trailing zero. The answer to 1.25 x 1.05 is 1.3125.

Mentor: Sounds like you've got the hang of it!