Answer:
Wind speed = 40 km/hr
Speed of the plane in still air = 280km/hr
Step-by-step explanation:
Formula to use
Distance = Rate multiplied by Time
D = R × T
Speed of the plane in still air = a
Speed of the wind = b
Plane with the wind (tailwind) is a + b where the time = 3hours
Plane against the wind is a - b, where the time = 4hours
This would give us 2 equations
3 × (a+ b) = 960
3a + 3b = 960 ...... Equation 1
4 × (a- b) = 960
4a - 4b = 960 ........ Equation 2
Solve this like you would with system of equations:
We solve the equation using elimination method.
Mulitply equation 1 by 4 and equation 2 by -3
4 × (3a + 3b = 960)
12a + 12b = 3840 ..... Equation 4
-3 × (4a- 4b = 960)
-12a + 12b= -2880 ........ Equation 5
Therefore we have
12a + 12b = 3840 ..... Equation 4
-12a + 12b= -2880 ........ Equation 5
24b = 960
b = 960÷ 24
b = 40
Wind Speed = 40km/hr
To find the speed of air, we use equation 2
4a - 4b = 960 ........ Equation 2
Substituting 40 which is wind of speed for b in equation 2 we would have
4a - 4(40) = 960
4a - 160 = 960
4a = 960 + 160
4a = 1120
a = 1120 ÷ 4
a = 280
The speed of the small plane in still air is 280 km/hr
