The answer is:
The dollar’s value becomes unstable.
Interest rates fluctuate in value.
During inflation, the value of our currency would be heavily depended on what the holders of our currency might do. (if they start to dump/sell our currency the value would drop, if they start to buy it the value would increase). Since we cannot control this, the value would become unstable.
Since interest rate is based on the percentage of the value of the currency, the interest rate would also fluctuates along with the value of the currency.