The ball's velocity will be represented by the derivative of its distance function:

Now find the times

for which this is equal to 30, i.e. solve

This has two solutions,

, but only one is positive and falls in the interval
![[0,3]](https://tex.z-dn.net/?f=%5B0%2C3%5D)
. So the velocity reaches 30 cm/s when

.
i think the person below me is correct and the answer is 12
Answer:
7 means ones because it is the units
Step-by-step explanation:
4= thousand
5= hundred
6= tens
7=ones / unit
<span>Step 1: 0.4 = 4⁄10</span>
<span>Step 2: Simplify 4⁄10 = 2⁄5</span>
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