How come bond prices go down when interest rates go up

is a question clogging my email. So here's the deal. Let us suppose you are going to sell a one year bond to the public that pays 10% interest. BUT the ten percent is taken off the top, meaning that you sell this ten percent bond for $90 (rounding off for simplicity). The purchaser will get $100 at redemption time. Suppose rates go UP to 20% and you sell another bond.....the price of the new bond will go down to $80. Interest is deducted but the buyer will still receive $100 on redemption---$80 plus the interest. So whenever rates go up the price of bonds go down. Whenever rates go down, the price of bonds go up.