Geometry

What kind of a mind can't do simple addition and subtraction, and thus multiplication and division, but instantly understands geometry?

I'm confused.

My kid has struggled with basic math. Still uses his fingers to add and subtract. Two weeks ago he started on decimals and fractions with common denominators, and got it right away. This week he started on geometry (using the "basic skills series - math topics - grade 5 workbook) and again, got it right away. He insisted on using an algebra equation to figure out the missing angle of a parallelagram!

I hope this isn't temporary!