For this use of the balance scale, assume that all pre-measured weights will go into the left pan of the scale. (In SP202, we will put weights on both sides of the scale.)

How many weights do you need in order to measure any exact number of ounces from one up to at least 120 ounces?

• Make a list of the weights you need
• Obviously, we need a one-ounce weight
• Write down one (1)
• Look at two ounces! Can you weigh it with any combination of (1)? No, you can't, so write down two (1,2)
• Look at three ounces! Same question? Yes, 1+2=3, so don't write anything down (1,2)
• Look at four ounces! Same question? No, you can't, so write down "4" (1,2,4)
• Keep doing this until you see a pattern.

• Read 'binary numbering system' in your book
• Calculate: 2^0=? 2^1=? 2^2=?
• Do these numbers look familiar?