Answer:
r=3 ft
Step-by-step explanation:
it is similarity of two triangles
one
perpendicular side=10 ft
base=10/2=5 ft
second
perpendicular side=10-4=6 ft
Base r=?
It is a simple problem where 120 centimeters need to be increased by 24%. The increased length can be found by:
120 * (24/100)
= 12 * (24/10)
= 288/10
= 28.8 centimeters
Then the total length of increase = 28.8 cm
Then the increased length = (120 + 28.8) cm
= 148.8 cm
So the length becomes 148.8 cm after it is increased by 24%.
Answer:
b 2/7
Step-by-step explanation:
Because there is a 6/21 chance and 2/7=6/21
Substitute the values into the inequality:
-1 - 1 > 0
-2 > 0
False
OK, so the graph is a parabola, with points x=0,y=0; x=6,y=-9; and x=12,y=0
Because the roots of the equation are 0 and 12, we know the formula is therefore of the form
y = ax(x - 12), for some a
So put in x = 6
-9 = 6a(-6)
9 = 36a
a = 1/4
So the parabola has a curve y = x(x-12) / 4, which can also be written y = 0.25x² - 3x
The gradient of this is dy/dx = 0.5x - 3
The key property of a parabolic dish is that it focuses radio waves travelling parallel to the y axis to a single point. So we should arrive at the same focal point no matter what point we chose to look at. So we can pick any point we like - e.g. the point x = 4, y = -8
Gradient of the parabolic mirror at x = 4 is -1
So the gradient of the normal to the mirror at x = 4 is therefore 1.
Radio waves initially travelling vertically downwards are reflected about the normal - which has a gradient of 1, so they're reflected so that they are travelling horizontally. So they arrive parallel to the y axis, and leave parallel to the x axis.
So the focal point is at y = -8, i.e. 1 metre above the back of the dish.
