To add and subtract unlike fractions, find the LCM of the denominators and convert them to equivalent like fractions. You don't have to do anything to fractions to multiply them, but you may need to reduce one after multiplying. To do that, find the GCF of the numerator and the denominator and divide both of them by it. If the GCF is 1, the fraction is in its simplest form.
Knowing the LCM of the denominators will help you to find a least common denominator of unlike fractions, which will allow you to add and subtract them successfully. Knowing the GCF and LCM will not help you in multiplying them, but knowing the GCF of the numerator and denominator of a fraction will help you reduce it if necessary.
multiply first, and then add
you are suppose to MULTIPLY on area.
You have to multiply to find area you have to add to find perimiter
you can multiply 281 and 3 you can add 840 and 3
You multiply (or divide), not add.