Train A has a speed 20 miles per hour greater than that of train B. If train A travels 270 miles in the same times train B travels 210 miles, what are the speeds of the two trains?

speed of train A = 70 + 20 = 90 miles per hour

speed of train B = 70 miles per hour 

Step-by-step explanation:

Let

speed of train B = a

speed of train A = a + 20

Recall

speed = distance/time

The travel time is same for both train. Therefore, let us make time subject of the formula in the speed equation.

Time = distance/speed

270/a + 20 = 210/a

cross multiply

270a = 210(a + 20)

270a = 210a + 4200

270a - 210a = 4200

60a = 4200

divide both sides by 60

a = 4200/60

a = 70

speed of train A = 70 + 20 = 90 miles per hour

speed of train B = 70  miles per hour

9514 1404 393

  F

Step-by-step explanation:

If the circle is tangent to the x-axis at 4, the center lies on the line x=4.

If the circle is tangent to the y-axis at 4, the center lies on the line y=4.

If the center of the circle is (x, y) = (4, 4) and it is tangent to the axes, then the radius is 4.

The standard-form equation of the circle centered at (h, k) with radius r is ...

  (x -h)² +(y -k)² = r²

For the values (h, k) = (4, 4) and r = 4, the equation is ...

  (x -4)² +(y -4)² = 16 . . . . . . matches choice F