7c would be 28 x 24 = ( 28 x 25 ) - ( 28 x 1 )
70 you solve by making a proportion 2.8/x =4/100
Answer:
Step-by-step explanation:
Because the price is constant we know the ratio of cost to number of books is constant.
x/14=13/4
x=14(13)/4
x=45.50
Leah paid $45.50 for 14 books.
Step-by-step explanation:
speed: 510mph
50 min = 5/6 hours
distance = 510 x 5/6 = 425miles
Topic: distance speed time
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Answer:
(c) 1.6
Step-by-step explanation:
Given, xy = 20 and both x, y are functions of t.
So,
⇒ ![\frac{d(xy)}{dt} = x\frac{dy}{dt} + y\frac{dx}{dt}](https://tex.z-dn.net/?f=%5Cfrac%7Bd%28xy%29%7D%7Bdt%7D%20%3D%20x%5Cfrac%7Bdy%7D%7Bdt%7D%20%2B%20y%5Cfrac%7Bdx%7D%7Bdt%7D)
now, when x = 4, y will be 5 as xy = 20.
by subtituting the values in above equation, we get;
⇒
⇒ ![0 = -8 + 5\frac{dx}{dt}](https://tex.z-dn.net/?f=0%20%3D%20-8%20%2B%205%5Cfrac%7Bdx%7D%7Bdt%7D)
⇒ ![\frac{dx}{dt} = \frac{8}{5}](https://tex.z-dn.net/?f=%5Cfrac%7Bdx%7D%7Bdt%7D%20%3D%20%5Cfrac%7B8%7D%7B5%7D)
⇒ ![\frac{dx}{dt} = 1.6](https://tex.z-dn.net/?f=%5Cfrac%7Bdx%7D%7Bdt%7D%20%3D%201.6)