Answer: it will take them 48 minutes.
Step-by-step explanation:
John can mow a lawn in 80 minutes. This means that the rate at which he moans the lawn per minute is 1/80
Rocky can mow the same lawn in 120 minutes. This means that the rate at which Rocky can mow the same lawn per minute is 1/120
If they work together, they would work simultaneously and their individual rates are additive. This means that their combined working rate would be
1/80 + 1/120 = 200/9600 = 1/48
Assuming it takes t hours for both of them to clean the room working together, the working rate per hour would be 1/t. Therefore,
1/48 = 1/t
t = 48 minutes
We can set it up like this, where <em>s </em>is the speed of the canoeist:
To make a common denominator between the fractions, we can multiply the whole equation by s(s-5):
![s(s-5)[\frac{18}{s} + \frac{4}{s-5} = 3] \\ 18(s-5)+4s=3s(s-5) \\ 18s - 90+4s=3 s^{2} -15s](https://tex.z-dn.net/?f=s%28s-5%29%5B%5Cfrac%7B18%7D%7Bs%7D%20%2B%20%5Cfrac%7B4%7D%7Bs-5%7D%20%3D%203%5D%20%5C%5C%2018%28s-5%29%2B4s%3D3s%28s-5%29%20%5C%5C%2018s%20-%2090%2B4s%3D3%20s%5E%7B2%7D%20-15s)
If we rearrange this, we can turn it into a quadratic equation and factor:
Technically, either of these solutions would work when plugged into the original equation, but I would use the second solution because it's a little "neater." We have the speed for the first part of the trip (9 mph); now we just need to subtract 5mph to get the speed for the second part of the trip.
The canoeist's speed on the first part of the trip was 9mph, and their speed on the second part was 4mph.
9514 1404 393
Answer:
- 6x +y = -6
- 6x -y = 8
- 5x +y = 13
Step-by-step explanation:
To rewrite these equations from point-slope form to standard form, you can do the following:
- eliminate parentheses
- subtract the x-term
- subtract the constant on the left
- if the coefficient of x is negative, multiply by -1
Of course, any operation you do must be done <em>to both sides of the equation</em>.
__
1. y -6 = -6(x +2)
y -6 = -6x -12 . . . . . eliminate parentheses
6x +y -6 = -12 . . . . . add 6x
6x +y = -6 . . . . . . . . add 6
__
2. y +2 = 6(x -1)
y +2 = 6x -6
-6x +y +2 = -6
-6x +y = -8
6x -y = 8 . . . . . . . . multiply by -1
__
3. y -3 = -5(x -2)
y -3 = -5x +10
5x +y -3 = 10
5x +y = 13
_____
<em>Additional comment</em>
The "standard form" of a linear equation is ax+by=c for integers a, b, c. The leading coefficient (generally, 'a') should be positive, and all coefficients should be mutually prime (have no common factors). That is why we multiply by -1 in problem 2.
There is a positive, linear relationship between the correct and guessed calories. The guessed calories for 5 oz. of spaghetti with tomato sauce and the cream-filled snack cake are unusually high and do not appear to fit the overall pattern displayed for the other foods. The correlation is r = 0.825 . This agrees with the positive association observed in the plot; it is not closer to 1 because of the unusual guessed calories for spaghetti and cake. The fact that the guesses are all higher than the true calorie count does not influence the correlation. The correlation r would not change if every guess were 100 calories higher. The correlation r does not change if a constant is added to all values of a variable because the standardized values would be unchanged. The correlation without these two foods is r = 0.984 . The correlation is closer to 1 because the relationship is much stronger without these two foods.
