Aduck waddles 3 meters east and then 4 meters north. what is the magnitude and direction of his displacement?

East is our x axis 
north is out y axis                               N
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                                                W |E
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                                                              S
so he moves 3 m to the right and then 4 upwards

imagine what that looks like a right angle triangle 

therefore we can use Pythagorean theorem  
 let the unknown side be x, which is the hypotenuse in this case

x^2 = 3^2 + 4^2 
x^2 = 9 + 16
x^2 = 25
take the square root
x = 5

5 is your magnitude and the direction is NE( North East) or positive direction