3rd grade math
posted by steph on .
A rectangle measures 30 feet by 20 feet and has a post at each corner. If posts are placed 2 feet apart. How many posts will there be in all?

I would have to find a piece of graph paper and draw it out for myself! But let me see if this is right:
All totaled, there would be 100 feet of fencing, so it seems there would be 50 posts. BUT 4 of those posts (the corner posts) would be counted twice, right?
So is this right?
30+30+20+20 = 100
100/2 = 50
50  4 = ?? 
If you start at one corner, it is 100 feet around, so each 2 feet place a post, or 50 posts.
To visualize this, sketch a 20x30 rectange, and place a post every 10 feet. Count the posts. You get 100/10=10 posts. 
how many packages of ribbon will sarah buy?

I definitely know the answer to that one, luis. It's probably around 58,007,450 packages of ribbon.