Answer:
The first car was traveling 70 mph, while the second was driving 50 mph.
Step-by-step explanation:
Set the cars as a proportion:
X represents the speed of the second car. By cross multiplying, you get the following equation:
You solve by distributing 150 to get 210x = 150x + 3000.
Solving for x gets you 50.
That means the first car was going at 50 mph. Adding 20, you get 70 as the speed for the second car.
Sum/difference:
Let
This means that
Now, assume that is rational. The sum/difference of two rational numbers is still rational (so 5-x is rational), and the division by 3 doesn't change this. So, you have that the square root of 8 equals a rational number, which is false. The mistake must have been supposing that
was rational, which proves that the sum/difference of the two given terms was irrational
Multiplication/division:
The logic is actually the same: if we multiply the two terms we get
if again we assume x to be rational, we have
But if x is rational, so is -x/15, and again we come to a contradiction: we have the square root of 8 on one side, which is irrational, and -x/15 on the other, which is rational. So, again, x must have been irrational. You can prove the same claim for the division in a totally similar fashion.