Expert: John Zalewski - 6/9/2009

Question
I am trying to figure how to solve decimals with nothing to borrow from.  Ex... 0.0025 - 0.075, 0.9- 76.78, 6.241 - 37.7293.  I have seen the answers and used a calculator but, I don't understand how 0.0025- 0.075= 0.075. I saw one website that renamed the first zero with a 7 on several problems.  Why would you do that? Please help. How do you subtract decimals with nothing to borrow from?


Answer
Hello, Taina.

When subtracting decimals, you need to line up the decimal points.

However, for your questions, you are subtracting larger decimals from smaller decimals. .075 is a larger number than .0025. To answer this question, first subtract .0025 from .075. Whatever is left is your answer, but it is negative.

To subtract .0025 from .075, you need to line up the decimal points. So you would have .0750-.0025.

For the ten-thousandths column, you can't subtract 5 from 0, so you will need to borrow from the thousandths column. Cross out the 5 in the tens column, and change it to a 4. Put the 1 that you borrowed from the thousandths column in the ones column, so that instead of 0 you will have 10.

Now you can subtract: .07(4)(10)-.0025.

For the ten-thousandths column, 10-5 = 5; for the thousandths column, 4-2 = 2.

For the hundredths column, 7-0 = 7. For the tenths column, 0-0 = 0.

Answer: -.0725

Hope this helps. The other problems are done similarly. If you have additional questions, please ask.

Regards,
John