She made her mistake at the first step. To simplify a radical, you would find two numbers that multiply by each other to get your original number (under the radical)
and have one of the number be a perfect square.
Her reasoning is wrong because 10*10 is not

. Had she been correct, her answer should have been able to be squared to equal

In other words, she should have done

(We used 25 because 25 is a perfect square, 5*5=25).
:)
We can solve it two ways, we´ll do it via physics:
We know that:
d=vt
d=770km/h*15h
d=11550km
Now at 660km/h:
t=d/v
t=11550km/660km/h
t=17,5h
Math way:
770km/h→15h
660km/h→x
So:
(770*15)/660=x
x=17,5h
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➷ Use this formula:
density = mass / volume
Rearrange it for mass:
mass = density x volume
Substitute the values in:
mass = 100 x 19.3
Solve:
mass = 1930g
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➶ Hope This Helps You!
➶ Good Luck (:
➶ Have A Great Day ^-^
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It is not because always remember, a positive is greater than a negative. This equation is showing a negative being greater than a positive. That's like saying I'm taller than you.
To find the value of r
We will follow the steps below
Usinf the equation of a slope:
slope(m) =

from the question given;
m= -3/4
x₁ = 3
y₁=4
x₂=-1
y₂=r
substituting the values into the slope formula

we can now simplify and then solve for r

cross-multiply
-3 x -4 = 4(r-4)
12 = 4(r-4)
Divide both-side of the equation by 4

3 = r - 4
add 4 to both-side of the equation
3+4 = r-4+4
7 = r
r=7
Therefore the value of r is 7