He made a mistake in step #2. It seemed to be a trivial mistake because it involved signs, but it still had a great impact. Since step#2, his solution was already wrong.
Instead of
(-1)²-4(2)(-6) = 1 + 48 = 49
What he did is
(-1)²-4(2)(-6) = -1 + 48 = 47
50 divided by 8 = 6.25
1oz perfume = $6.25
110 divided by 17 = 6.4705
1oz perfume = $6.4705
Therefore the second option is cheaper
Answer:
Option (4).
Step-by-step explanation:
Outer diameter of the hollow metallic ball = 10 centimeters
Outer radius of this ball =
= 5 cm
Volume of the outer ball
= 
= 
Inner radius of the hollow metallic ball = (5 - 1) = 4 cm
Volume of the inner hollow ball
= 
Volume of the metal used in the metallic ball = 
= 
= ![\frac{4}{3}\pi [(5)^3-(4)^3]](https://tex.z-dn.net/?f=%5Cfrac%7B4%7D%7B3%7D%5Cpi%20%5B%285%29%5E3-%284%29%5E3%5D)
Therefore, expression given in option (4) will be used to measure the volume of the hollow metallic ball.
7 and 1/2 mile because 2,640=1.5 miles
4-1.5=2.5+5=7.5