6. The angles of a quadrilateral are in the ratio $3: 4: 5: 6$.
What is the difference between the largest angle and the smallest angle?
A $30^{\circ}$
B $40^{\circ}$
C $50^{\circ}$
D $60^{\circ}$
E $70^{\circ}$
6. D The sum of the interior angles of a quadrilateral is $360^{\circ}$. So the smallest angle in the quadrilateral is $3 \times \frac{360^{\circ}}{3+4+5+6}=60^{\circ}$ and the largest angle is $6 \times \frac{360^{\circ}}{3+4+5+6}=120^{\circ}$. Hence the required difference is $60^{\circ}$.