an air force plane left rome at the same time as a jet the planes flew in opposite direction。

Question

The jet flew at a speed of 420 km/h. After ten hours they were 8000 km apart. How fast did the air fore plane fly?

Answer 1

jet: 10(420) = 4200 km

air: 10r = 10r

 

4200 + 10r = 8000

 

Can you solve for r and answer?

Answer 2

Hi Sihui, use the D(istance) = R(ate) * T(ime) equation to solve this.

 

Equation for jet:

 

D_j = R_j * T_j

 

D_j = 420 * 10, or 4200 kilometers.

 

Equation for air force plane:

 

D_a = R_a * T_a

 

D_a = 8000 - 4200, or 3800 kilometers, because the jet covered 4200 kilometers of the 8000 kilometers.

 

T_a = T_j = 10

 

R_a =3800 /10, or 380 kilometers per hour.

 

Questions?

Answer 3

Let x = the speed of the air force plane.

 

distance = rate·time

• distance = 8000 km
• rate = separation rate of the two aircraft = 420 + x
• time = 10 hours

 

8000 = (420 + x)·10

800 = 420 + x

 

Solve for x