Question 1143354
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It takes her 2 minutes to fill the jar to 50%.  1 penny goes in the jar.<br>
In the next two minutes, she fills half of the 50% that is left to fill; half of 50% is 25%, so the jar is 75% full.  That means 25% is empty; which is less than 30%.<br>
So the 2nd penny would have gone in the jar at the end of those 2 minutes, when the jug had 25% empty space left.  That means that, at the instant the jug has less than 30% empty space left, there is only 1 penny in the jar.<br>
ANSWER: 1 penny in the jar at the instant the jug has less than 30% empty space.