Answer:
1395 times.
Step-by-step explanation:
The Williams family open their door 28 + 17 = 45 times a day.
So in October they opened it 31 * 45 = 1395 times.
Answer:
9 · x - 16
Explanation:
Nine times a number: 9 · x
Decreased by 16: - 16
Put them together: 9 · x - 16
H=0
Therefore:
144t-16t²=0
t (144-16t)=0
We have two equations:
1)
t=0 (when the ball is released)
2)
144-16t=0
-16t=-144
t=-144 / -16=9 (this is the time )
Answer: the ball hit the ground in 9 s.
