The answers are 5 x (80 x 7) and 80 fives plus 7 fives
His car gets 21 mpg (miles per gallon). With 1 gallon he can drive 21 miles. For example, with 10 gallons, he can drive 21 mpg * 10 gal = 210 miles.
He bought $19.50 worth of gas at $1.40 per gallon.
$19.50 / ($1.40/gal) = 13.93 gal
He already had 5 gal of gas in his tanks, so now he has
5 gal + 13.93 gal = 18.93 gal
With 18.93 gal, he can drive
18.93 gal * 21 mpg = 292.5 miles
Answer:
7920 yards
Step-by-step explanation:
just use a calculator next time. Do miles to yards converter in :)
The area of the triangle is
A = (xy)/2
Also,
sqrt(x^2 + y^2) = 19
We solve this for y.
x^2 + y^2 = 361
y^2 = 361 - x^2
y = sqrt(361 - x^2)
Now we substitute this expression for y in the area equation.
A = (1/2)(x)(sqrt(361 - x^2))
A = (1/2)(x)(361 - x^2)^(1/2)
We take the derivative of A with respect to x.
dA/dx = (1/2)[(x) * d/dx(361 - x^2)^(1/2) + (361 - x^2)^(1/2)]
dA/dx = (1/2)[(x) * (1/2)(361 - x^2)^(-1/2)(-2x) + (361 - x^2)^(1/2)]
dA/dx = (1/2)[(361 - x^2)^(-1/2)(-x^2) + (361 - x^2)^(1/2)]
dA/dx = (1/2)[(-x^2)/(361 - x^2)^(1/2) + (361 - x^2)/(361 - x^2)^(1/2)]
dA/dx = (1/2)[(-x^2 - x^2 + 361)/(361 - x^2)^(1/2)]
dA/dx = (-2x^2 + 361)/[2(361 - x^2)^(1/2)]
Now we set the derivative equal to zero.
(-2x^2 + 361)/[2(361 - x^2)^(1/2)] = 0
-2x^2 + 361 = 0
-2x^2 = -361
2x^2 = 361
x^2 = 361/2
x = 19/sqrt(2)
x^2 + y^2 = 361
(19/sqrt(2))^2 + y^2 = 361
361/2 + y^2 = 361
y^2 = 361/2
y = 19/sqrt(2)
We have maximum area at x = 19/sqrt(2) and y = 19/sqrt(2), or when x = y.
The value of x that will make this equation true is 50.
0.5 times 50=25 -8 = 17
0.2 times 50= 10 +7 = 17
Therefore, your answer is 50.
