Let the speed of river be x km/hr down stream.
Time = Distance / speed
Since river flows downstream, speed of boat down stream = Speed of boat + speed of river = (15 + x).
Since river flows downstream, speed of boat upstream = Speed of boat - speed of river = (15 - x).
Time Upstream - Time Downstream = 75 minutes
Time Upstream = 45 / (15 - x)
Time Downstream = 45 / (15 + x)
75 minutes = 75/60 = 5/4 hours
Time Upstream - Time Downstream = 75 minutes = 5/4 hours
45 / (15 - x) - 45 / (15 + x) = 5/4 Divide both sides by 45
1 / (15 - x) - 1 / (15 + x) = (5/4)*(1/45)
1 / (15 - x) - 1 / (15 + x) = 1/36
((15 + x) - (15 -x)) / (15-x)(15+x) = 1/36
(15 +x - 15 +x) / (15-x)(15+x) = 1/36
2x / (15-x)(15+x) = 1/36
(15-x)(15+x) = 2x*36
(15-x)(15+x) = 72x
225 - x² = 72x
0 = x² + 72x -225
x² + 72x -225 = 0 This is a
quadratic function, use a calculator that can solve the function, by
inputting the function.
x = 3, or -75. Since we are solving for speed, we can not have negative values.
x = 3 is the only valid solution.
Speed of the river = 3 km/hr downstream.
Copyright.
10, 20w, 2w, and we are factors of 20w and 40wz
Answer:
(0 2,3,5)
Step-by-step explanation:
Domain is the x factor of every relation
Answer:
20% alcohol = 1 gal
10% alcohol = 9 gal
Step-by-step explanation:
Let
x = 20% alcohol
y = 10% alcohol
x + y = 10 (1)
0.20x + 0.10y = 10*0.11
0.20x + 0.10y = 1.1 (2)
From (1)
x = 10 - y
Substitute x = 10 - y into (2)
0.20x + 0.10y = 1.1
0.20(10 - y) + 0.10y = 1.1
2 - 0.20y + 0.10y = 1.1
- 0.20y + 0.10y = 1.1 - 2
-0.10y = -0.9
y = -0.9/-0.10
y = 9 gal
substitute y = 9 into (1)
x + y = 10
x + 9 = 10
x = 10 - 9
x = 1 gal
20% alcohol = 1 gal
10% alcohol = 9 gal
