She can expect to pick a black marble 125 times
Alright first ranks doesn’t mean they’ll get it right. It just means how active the user is.
Now to answer your problem, c is given to be 0.5.
So 5(0.5) is the same as 5/2, which is 2.5.
So 10-2.5=7.5
The nail will stick to the magnet because it will become magnetized.Also because the north pole in the magnet rearranges the magnet domains inside the steel so that their south poles all point toward the north pole of the permanent magnet
