Answer:the plane in still air is 904 km/h
the rate of the wind is 104 km/h
Step-by-step explanation:
Let x represent the rate or speed of the plane in still air.
Let y represent the rate or speed of the wind.
Flying against the wind, an airplane travels 4000 kilometers in 5 hours. This means that the total speed of the airplane would be (x - y) km/h
Distance = speed × time
Therefore
4000 = 5(x - y)
4000 = 5x - 5y - - - - - - - - -1
Flying with the wind, the same plane travels 5040 kilometers in 4 hours. This means that the total speed of the airplane would be (x + y) km/h. Therefore,
5040 = 4(x + y)
5040 = 4x + 4y - - - - - - - - - 2
Multiplying equation 1 by 4 and equation 2 by 5, it becomes
16000 = 20x - 20y
20160 = 20x + 20y
Subtracting, it becomes
- 4160 = - 40y
y = - 4160/-40
y = 104
Substituting y = 104 into equation 1, it becomes
4000 = 5x - 5 × 104
4000 = 5x - 520
5x = 4000 + 520
5x = 4520
x = 4520/5 = 904
Let the amount invested with 5% interest be x
Therefore, the amount invested with 6% interest will be (6000-x)
It is given that the total interest earned yearly is $337.5. Thus, the equation of interest will be:
Multiplying both sides by 100 we get:
Subtracting both sides by 36000 we get:
Thus, the amount invested at 5% is $2250
Therefore, the amount invested at 6% will be $(6000-2250)=$3750
Answer:
8
Step-by-step explanation:
2+6m+7=57
6m=57-7-2
6m=50-2
6m=48
m=48/6
m=8
7+5= 12 ones. Or one ten and 2 ones. They made 12.
