Question 321880
1. A small plane went 240 miles in 3 hours flying against the wind and the same amount of time to go 300 miles with the wind. What was the speed of the plane without the wind?
240/3 = 80 mph
300/3 = 100 mph
The airspeed of the plane is the average, 90 mph.
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2. It takes Danny 3 times as long to mow a field as it takes his father. Together they can mow the same field in 4 hours. How long does it take Danny working alone? 
Danny takes 3x hours
Father takes x hours
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Danny does 1/3x of the field per hour.
His father does 1/x per hour.
Together, they do 1/(3x) + 1/x per hour, = 4/(3x) fields per hour.
4/(3x) fields per hour --> 3x/4 hours per field
3x/4 = 4
3x = 16
x = 16/3
Danny takes 3x, = 16 hours.