Let the exterior angle be x, then interior angle will be 4x
We know that,
Interior angle + Exterior angle = 1800
∴x+4x=1800
x=1805=360
Interior angle = 4x=4×360=1440
We know that,
Interior angle of a polygon =(n−2)n×1800
1440=(n−2)n×1800
1440n=1800n−3600
1800n−1440n=3600
360n=3600
∴ n = 10
So, number or sides = 10