Answer
$B=0.020T$
Work Step by Step
Magnetic flux is equal to $$\Phi_B=BAcos\theta$$ Since the area of a rectangle equals $A=lw$, the formula becomes $$\Phi_B=Blwcos\theta$$ Solving for magnetic field strength $B$ yields $$B=\frac{\Phi_B}{lwcos\theta}$$ Substituting known values of $\Phi_B=4.8\times 10^{-5} T \times m^2$, $l=5.1cm=0.051m$, $w=6.8cm=0.068m$, and $\theta=47^{\circ}$ yields a magnetic field strength of $$B=\frac{4.8\times 10^{-5} T \times m^2}{(0.051m)(0.068m)cos(47^{\circ})}=0.020T$$
