During which time interval was the motion fastest?

a.1 h to 2 h

b.2 h to 3 h

c.3 h to 4 h

d.4 h to 5 h

D.4 h to 5 h

Explanation:

The velocity of an object is defined as

where

d is the displacement

t is the time

In a displacement-time graph, such as the one in the figure, the velocity of the object corresponds to the slope of the curve. We see that in this graph, the part where the slope is steeper is between 4h and 5h, so this is the moment where the object is moving faster.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form