10. Given that the largest angle of an isosceles triangle is 4 times the smallest angle, then the difference between the largest and smallest angles is $(\quad)$ degrees.
【Analysis】First case:
$$
180^{\circ} \div(4+1+1)=30^{\circ}, \quad 30^{\circ} \times(4-1)=90^{\circ}
$$

Second case:
$$
180^{\circ} \div(4+4+1)=20^{\circ}, \quad 20^{\circ} \times(4-1)=60^{\circ}
$$

There are two solutions: $90^{\circ}$ or $60^{\circ}$