A bag full of beads

You own a small craft store, and one day a customer comes into your store looking to purchase 270 grams of plastic beads so her kids can make necklaces.  Although you find it to be rather strange that she would want such an exact weight, you are keen to make the sale so you don't question her request.

The problem is that all you have is a bag filled with hundreds of small plastic beads of equal size and weight but you don't know how much each bead weighs.  The only thing you know is that ALL the beads in the bag together weigh exactly 720 grams (without the bag).

Using only a traditional balance scale (pictured above), describe how you can accurately weigh out 270 grams of beads to sell to your customer.

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SOLUTION FROM LAST WEEK:

Turn on any 2 of the switches and leave them on for 10 minutes.  Then, turn one of those switches back to the "off" position.  Quickly head upstairs to the other room.  Since only 1 of the switches was left in the "on" position, then this switch matches up with the only light bulb that is currently on.  Of the 2 bulbs that are off, the one that is hot to the touch will go with the switch that you turned off right before, and the one that is cold will go with the switch that you never turned on.