Convert 21 cm to inches. Show your dimensional analysis setup. Know the first part, but am having trouble with the second part..Help please?

3 Answers

Relevance
  • 4 years ago
    Favorite Answer

    cm x (in/cm) = in

    21 cm x (1 in / 2.54 cm) = 8.3677 in

    • Login to reply the answers
  • 4 years ago

    There are 2.54 cm in 1 inch. This will be the conversion factor ( fraction) that you will multiply by. How do you know which goes on the top and which goes on the bottom of the fraction? It varies from problem to problem. Decide what word you want to get rid of (cm in this case). You write the conversion factor so that cm will cancel out: 21 cm x (1 inch/2.54 cm) = 8.27 inches. Dimensional analysis is really your friend. If the words "cm" cancel out, and your answer comes out in inches, as expected, you can be pretty sure that the number is right also.

    • Login to reply the answers
  • Al
    Lv 7
    4 years ago

    21 in x 1/2.54 cm/in

    • Login to reply the answers
Still have questions? Get your answers by asking now.