The mass number is an average of the masses of all naturally occurring isotopes of an element true or false

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space

Give one example of a pure (exact) number and of an estimated (measured) number.

When microscope slides are stained to show blood cells, the small red blood cells that appear on the slides are much numerous than the large white blood cells. this supports the concept that