Answer:
- rate of the boat in still water = 6.5 miles / hour
- rate of the current = 2.5 miles / hour.
Explanation:
<u>1) Name the two variables:</u>
- b: rate of the boat in still water:
With that, the net rates of the boat down the river and upstrean are:
<u>2) Now set the equations for the distance as a function of the times and the rates:</u>
- downstream: 18 miles = (b + c) × 2 hours
- upstream: 18 miles = (b - c) × 4.5 hours
<u>3) Set the system of equations:</u>
- 18 = 2(b + c) ⇒ 9 = b + c . . . Equation (1)
- 18 = 4.5 (b - c) ⇒ 4 = b - c . . . Equation (2)
<u>4) Solve the system by </u><u>elimination</u><u>:</u>
- Add equations (1) and (2): 9 + 4 = 2b
- Divide both sides by 2: 13/2 = b
- Replace b with 6.5 in equation (2) and solve:
4 = 6.5 - c ⇒ c = 6.5 - 4 = 2.5
<u>5) Results:</u>
- b = rate of the boat in still water = 6.5 miles / hour
- c = rate of the current = 2.5 miles / hour.
Answer:
Decrease in temperature = 4.6714°C
Step-by-step explanation:
We know that the formula fro deflection is:
δ = PL/AE + LαΔT
As deflection is equal to zero in this case, the formula becomes
ΔT = -P/αAE -------------- equation (1)
Now,
we see that only vertical force acting is weight
W = mg = 100*9.81
W = 981N = ∑
where 1N = 1kgm/s²
Now,
for horizontal forces
As we know that, Sum of all horizontal forces = 0
P - μN = 0
P - μW = 0
P = μW
P = 0.6 * 981
P = 588.8N or 589N
Now we need to calculate the area
area = width * thickness = 20 * 3
area = 60 mm²
Now by substituting all these values in equation 1, wee get
ΔT = -P/αAE = - 588.6/(20*10⁻⁶*60*10⁻⁶*105*10⁹)
ΔT = - 4.6714°C (negative sign indicates decrease)
Answer: D. n + q = 20
5n + 25q = 300
Step-by-step explanation:
Let n represent the number of nickels that you have.
Let q represent the number of quarters that you have.
Suppose you have 20 coins. It means that
n + q = 20
The total value of the coins is $3. The value of a quarter is $0.25 and the value if a nickel is $0.05. Therefore, the equation would be
0.05n + 0.25q = 3
Multiplying both sides of the equation by 100, it becomes
5n + 25q = 300
The correct option is
D. n + q = 20
5n + 25q = 300
