Explanation

To join the two tracks, we need to take two points on one track and one point on the other to form a triangle; we cannot use three points from one track. Since the order of the points doesn't matter, we use the formula for combinations.

We can take 2 points from the first track and 1 point from the second =^{6}C_{2} * ^{10}C_{1} = 150 ways.
We can take 1 point from the first track and 2 points from the second = ^{6}C_{1} * ^{10}C_{2} = 270 ways.

Thus, the total number of ways of forming a triangle is 150 + 270 = 420.

**The correct choice is E.**

We can take 2 points from the first track and 1 point from the second =

Thus, the total number of ways of forming a triangle is 150 + 270 = 420.

Three points where two lines meet…