90 is a tenth of 900. You need ten 90's to make 900.
        
             
        
        
        
16*28=448
28 is 12 inches higher than 16 so it should work.
        
                    
             
        
        
        
Answer:
5mph
Step-by-step explanation:
Let speed of boat in still water is s.
Distance proportional to speed
90/10 = (s+ 4)/(s - 4)
=> 9s - 36 = s + 4
=> 8s = 40
=> s= 5 mph
:-)
 
        
             
        
        
        
Answer:
he will use 2 posts.
Step-by-step explanation:
the two posts together will make 1 foot, so with one post on each endof the 7 foot deck, that leaves 6 feet between them.
 
        
                    
             
        
        
        
Answer:
Step-by-step explanation:
Vertex form is accomplished by completing the square on the quadratic. Do this by first setting the parabola equal to 0 then moving the constant over to the other side:

Now take half the linear term, square it, and add it to both sides. Our linear term is 6. Half of 6 is 3, and 3 squared is 9:

The reason we do this is to create a perfect square binomial on the left:
 (obviously the 0 results from the addition of 9 and -9). Move the 0 back over to the other side and set the quadratic back equal to y:

This gives you a vertex of (-3, 0), which is a minimum value, since the parabola opens upwards.