Question

Flying with the wind, a plate went 251 km/h. Flying into the same wind, the plane only went 219 km/h. What is the speed of the wind?
A. 8 km/h
B. 15 km/h
C. 26 km/h
D. None of the above.

Answer 1

Answer: Option D, the actual speed of the wind is 16km/h.

Step-by-step explanation:

Let's define two quantities:

Sp = Speed of the plane, that we assume it is constant.

Sw = Speed of the wind, that we assume it is constant.

When the plane flies with the wind, the total speed will be

Sp + Sw = 251km/h.

When the plane flies against the wind, the total speed will be:

Sp - Sw = 219km/h.

Then we have two equations:

Sp + Sw = 251km/h

Sp - Sw =  219km/h.

We want to find the speed of the wind, so we should isolate the speed of the plane in one of the equations, let's isolate it in the second equation:

Sp = 219km/h + Sw.

Now we can replace this into the other equation:

Sp + Sw = 251km/h.

(219km/h + Sw) + Sw = 251km/h.

2*Sw + 219km/h = 251km/h

2*Sw = 251km/h - 219km/h = 32km/h

Sw = (32km/h)/2 = 16km/h.

This is really close to the option B, but is not equal, so the correct answer will be D, none of the above.