8/10 = z/30 what does z equal

a train makes a trip at 65 mi/h. A plane traveling 130 mi/h makes the same trip in 3 fewer hours. Write and solve an equation to

Rudik [331]

The formula used for calculating the time is:

t = d / v

where t is time, d is distance and v is velocity

We know that the difference in the two times is 3 hours, therefore:

d / 65 – d / 130 = 3

Calculating for d:

d = 30 / (1/65 – 1/130)

<span>d = 3900 miles</span>

8 0

3 years ago

The graph h = −16t^2 + 25t + 5 models the height and time of a ball that was thrown off of a building where h is the height in f

Thepotemich [5.8K]

Answer:

part 1) 0.78 seconds

part 2) 1.74 seconds

Step-by-step explanation:

step 1

At about what time did the ball reach the maximum?

Let

h ----> the height of a ball in feet

t ---> the time in seconds

we have

$h(t)=-16t^{2}+25t+5$

This is a vertical parabola open downward (the leading coefficient is negative)

The vertex represent a maximum

so

The x-coordinate of the vertex represent the time when the ball reach the maximum

Find the vertex

Convert the equation in vertex form

Factor -16

$h(t)=-16(t^{2}-\frac{25}{16}t)+5$

Complete the square

$h(t)=-16(t^{2}-\frac{25}{16}t+\frac{625}{1,024})+5+\frac{625}{64}$

$h(t)=-16(t^{2}-\frac{25}{16}t+\frac{625}{1,024})+\frac{945}{64}\\h(t)=-16(t^{2}-\frac{25}{16}t+\frac{625}{1,024})+\frac{945}{64}$

Rewrite as perfect squares

$h(t)=-16(t-\frac{25}{32})^{2}+\frac{945}{64}$

The vertex is the point $(\frac{25}{32},\frac{945}{64})$

therefore

The time when the ball reach the maximum is 25/32 sec or 0.78 sec

step 2

At about what time did the ball reach the minimum?

we know that

The ball reach the minimum when the the ball reach the ground (h=0)

For h=0

$0=-16(t-\frac{25}{32})^{2}+\frac{945}{64}$

$16(t-\frac{25}{32})^{2}=\frac{945}{64}$

$(t-\frac{25}{32})^{2}=\frac{945}{1,024}$

square root both sides

$(t-\frac{25}{32})=\pm\frac{\sqrt{945}}{32}$

$t=\pm\frac{\sqrt{945}}{32}+\frac{25}{32}$

the positive value is

$t=\frac{\sqrt{945}}{32}+\frac{25}{32}=1.74\ sec$

8 0

3 years ago

If 1 cm represents 30 km on a map and colorado is shown by a 20cm by 15 cm rectangle on the map, what is the approximate actual

zubka84 [21]

Answer:

20*30km = 600km

15*30km = 450km

600km * 450km = 270000 km^2

Step-by-step explanation:

assuming 1cm --- 30km causes that 2cm --- 60km, 3cm --- 90km, 4cm --- 120km etc. Notice that number of km's is 30 times greater than the number of cm's on a map

using this logic, you calculate both real dimensions of Colorado by multiplying 20*30 = 600 km and 15*30 = 450km

Then we use a formula of an area of a rectangle $A=a\cdot b$ assuming $a=600km, \ b=450km$ and get $A=600\cdot 450=270000km^2$ which is an actual area of Colorado

3 0

2 years ago

4 is the square root of which number ?

Tom [10]

Your answer would be two

6 0

3 years ago

A sapling, or young tree, is planted in a garden. After 3 years, it is 180 cm tall. After 7 years, it is 368 cm tall. What is th

Mashcka [7]

The function modelled by the height (x) of the tree is as follows:
y - 180 = (368 - 180)/(7 - 3) (x - 3)
y - 180 = 47(x - 3) = 47x - 141
y = 47x - 141 + 180 = 47x + 39

Therefore, after 10 years, the tree will be 47(10) + 39 = 470 + 39 = 509 cm tall

8 0

3 years ago