# River Width Estimation Problem

• Meliora
In summary, Jean is trying to determine the width of a river by using a large rock as a reference point. She measures her stride to be one yard and the distance back to her camp is 120 strides. She also mentions using an angle of 30 degrees to measure the distance. The equation for this problem can be solved using trigonometry.

#### Meliora

1. Jean camps beside a wide river and wonders how wide it is. She spots a large rock on the bank directly across from her. She then walks upstream until she judges that the angle between her and the rock, which she can still see clearly, is now at an angle of 30 downstream (as shown in the figure). Jean measures her stride to be about one yard long. The distance back to her camp is 120 strides.

About how far across, in yards, is the river?

About how far across, in meters, is the river?

(there is also a diagram drawn up for this but I am unsure on how to include that in this post)

2. I am honestly unsure of any sort of equation in this case. I am taking intro to physics and my book still hasn't come in the mail yet. My instructor is very hard to understand, but possibly something utilizing the Pythagorean theorem?

3. I am not really sure where to even begin once I have established that one side is 120 yards in length. I feel like a complete idiot here, but this homework is due tonight at 10pm, and this is the last problem I need to complete the assignment.

Any help and pointers in the right directions would be greatly appreciated.

Hi Meliora! Welcome to Physics Forums!

try to attempt using trigonometry. go on and try to do something and show us your work. if you are stuck, we are here to help.

Thanks supratim1, I appreciate it.

Upon further investigation I realized how simple the solution to this problem is, hah. I guess I owe it to a brain fart.