You do it because if you added before you multiplied your answer would be way out in the atmosphere. I'm not sure who invented that though...
multiply first, and then add
you are suppose to MULTIPLY on area.
You multiply.
multiply
you can multiply 281 and 3 you can add 840 and 3
multiply first, and then add
you are suppose to MULTIPLY on area.
multiply
You multiply.
multiply
you can multiply 281 and 3 you can add 840 and 3
Multiply for the area, add for the perimeter.
you add
Add.
You multiply them.
multiply
You add for perimeter...