Speed of the boat = u
speed of the current = v
in downstream,
u - v = 105/5
u - v = 21
in upstream
u + v = 105/7
u + v = 15
add both equations
2u = 36
u = 18
v = -3
so
speed of the boat = 18 km/h
speed of the current = 3 km/h
The answer to the problem is d
Answer:
17x+5
Step-by-step explanation:
3x^2=9x
9x+8x+5
(9x+8x)+5
17x+5
Answer:
The perimeter of the dog's play area is 30 ft
Step-by-step explanation:
Rectangle:
- The opposite sides are congruent.
- The opposite angles are congruent.
- The sum of all four angles of a rectangle is 360°.
- The sum of two adjacent angles of a rectangle is 180°.
- The diagonals bisect each other.
- The perimeter of a rectangle is = 2(Length+width)
- The area of a rectangle is = Length × width
Given that,
The length of the long side of the dog's play area was = 10 ft.
So, Length of dog's play area is = 10 ft.
The length of the short side of the dog's play area was = 5 ft.
So, width of dog's play area is = 5 ft.
It is a rectangular plot.
So, the perimeter of the dog's play area is =2(Length+width)
=2(10+5) ft
=2(15) ft
=30 ft
(a) Average time to get to school
Average time (minutes) = Summation of the two means = mean time to walk to bus stop + mean time for the bust to get to school = 8+20 = 28 minutes
(b) Standard deviation of the whole trip to school
Standard deviation for the whole trip = Sqrt (Summation of variances)
Variance = Standard deviation ^2
Therefore,
Standard deviation for the whole trip = Sqrt (2^2+4^2) = Sqrt (20) = 4.47 minutes
(c) Probability that it will take more than 30 minutes to get to school
P(x>30) = 1-P(x=30)
Z(x=30) = (mean-30)/SD = (28-30)/4.47 ≈ -0.45
Now, P(x=30) = P(Z=-0.45) = 0.3264
Therefore,
P(X>30) = 1-P(X=30) = 1-0.3264 = 0.6736 = 67.36%
With actual average time to walk to the bus stop being 10 minutes;
(d) Average time to get to school
Actual average time to get to school = 10+20 = 30 minutes
(e) Standard deviation to get to school
Actual standard deviation = Previous standard deviation = 4.47 minutes. This is due to the fact that there are no changes with individual standard deviations.
(f) Probability that it will take more than 30 minutes to get to school
Z(x=30) = (mean - 30)/Sd = (30-30)/4.47 = 0/4.47 = 0
From Z table, P(x=30) = 0.5
And therefore, P(x>30) = 1- P(X=30) = 1- P(Z=0.0) = 1-0.5 = 0.5 = 50%
