math
posted by jane .
two cars leave the same point at noon. one car travels north and the other car travels east. suppose the northbound car is traveling 40mph, and after two hours, the two car are 100 miles apart.how fast is the other car going?

recall that speed is distance travelled over time.
let x = speed of the other car.
then we setup the equation.
when you draw the directions they're travelling, you will form a right triangle. thus recall that in a right triangle, the hypotenuse (in this the the distance between them which is 100 miles) is given by the Pythagorean theorem:
c^2 = a^2 + b^2
we equate distances:
100^2 = (40*2)^2 + (2x)^2
10000 = 80^2 + 4x^2
10000  6400 = 4x^2
3600 = 4x^2
x^2 = 900
x = 30 mph
hope this helps~ :) 
thanks