So,
If the number in the ten-thousandth's place is greater than or equal to 5, then round up. If not, round down.
0.1325: Note the 5. We round up.
0.1325 --> 0.133
(a-b)(a+b) because when you reverse the sum you do axa and ax-b xx
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
