A river current has a velocity of 5 km/h relative to the shore. A boat moves in the same direction as the current at 4 km/h relative to the river. How do you calculate the velocity of the boat relative to the shore?

Gunpowder residue is most likely to show up where on a shooters hands

Two students, each riding bicycles, start from the same apartment building and ride to the same building on campus, but each takes a different route. the first student rides 1100 m due east and then turns due north and travels another 1430 m before arriving at the destination. the second student heads due north for 1930 m and then turns and heads directly toward the destination.at the turning point, how far is the second student from the destination?

If anyone who can me with this hw? i would really appreciate it