If the earth shrinks to half its radii without changing its mass than what would be duration of day - Physics - System Of Particles And Rotational Motion

Question

If the earth shrinks to half its radii without changing its mass
than what would be duration of day?

nitish.gupta · Accepted Answer

Shrinking the Earth to half its radius would certainly have an
effect on it In order to conserve angular momentum, it will spin
faster than before (remember the skater analogy) and thus duration
of the day will be much smaller
It turns out that time period of rotation becomes, T = 45
minutes which would be duration of a day

If the earth shrinks to half its radii without changing its mass than what would be duration of day?