How do I know how many dpi's my image has and how can I change it? I have a mac, and I use photoshop elements.?

I need to resize my images for my portfolio to the School of Visual Arts in nyc. They ask that we scan our work and save them as separate files on a cd with no more dpi than 72 and no bigger than 600px in the longest direction. I have scanned the work, and I have resized them to fit the 600px requirement, however, I don't know how to change the dpi. help please.How do I know how many dpi's my image has and how can I change it? I have a mac, and I use photoshop elements.?
The easiest (and quickest) way to do this is to use the Crop Tool. Open your photos (it works best to open either all portrait or all landscape orientation) and click on the Crop Tool. Up in the Options Bar, set Aspect Ratio to Use Photo Ratio. Now, if you've open Portrait Orientation, the longest side will be the height so type 600 px in the Height box and press Enter. Type 72 in the Resolution box and make sure the units are pixels/inch. Click in a corner of your photo and drag to the opposite corner and release the mouse button. Click the green checkmark to commit the action and File%26gt;Save As.. so you don't overwrite the original and destroy it. You can do all the photos with Portrait Orientation without changing anything. When you switch to Landscape Orientation be sure to redo the Options Bar... especially make sure that you remove 600 px from the Height box.How do I know how many dpi's my image has and how can I change it? I have a mac, and I use photoshop elements.?
when you open your picture in PS, go to Image (in the tool bar)%26gt; then select Image size.



When the 'image size' window appear you can resize your picture using the width and hight values. As you require 600px, set the longest side value to 600 and select pixels in the drop down menu next to it.



Normally when you scan a picture it will be 300DPI (Dots/Pixels Per Inch).

To change your DPI set the resolution, which is the last option in the window, to your required value- 72 and in the drop down menu next to it, select pixel/inch



And you are done!