Answer:
The first and last one!!
Step-by-step explanation:
Was it correct?? Hope this helps!!(¬_¬ )
Answer:
Speed of plane in still air: 490 mile/hour
speed of wind: 70 mile/hour
Step-by-step explanation:
still speed = x wind speed = w
with wind: speed = still + wind
(x+w) * 3 = 1680 ...a
against wind: speed = still - wind
(x-w) * 4 = 1680 ...b
b-a ... 4x-4w-3x-3w = 0
x-7w = 0
x = 7w
substitution: (7w+w)*3 = 1680 8w = 560 wind speed (w) = 70
still speed (x) = 7w = 490 mile/hour
<span>they built 2.22 km per day I think</span>
That would be option A
because square root of 81 is 9 and square root m^6 is m^3.