Solving Physics Question: Momentum Change of 0.42 kg Ball

[draconicspectre]

A 0.42 kg ball is moving horizontally with a speed of 5.5 m/s when it strikes a vertical wall. The ball rebounds with a speed of 2.0 m/s. What is the magnitude of the change in linear momentum of the ball?

Might seem like a simple problem, but everytime i input an answer into it, it says I am wrong, can neone help?

 

[radou]

A 0.42 kg ball is moving horizontally with a speed of 5.5 m/s when it strikes a vertical wall. The ball rebounds with a speed of 2.0 m/s. What is the magnitude of the change in linear momentum of the ball?

Might seem like a simple problem, but everytime i input an answer into it, it says I am wrong, can neone help?

Since the change in linear momentum is a vector given by (mv2-mv1)i, its magnitude is the square root of (mv2-mv1)^2, which equals mv2-mv1. This should work.