A mass M is attached to an ideal massless spring. When this system is set in motion, it has a period T. What is the period if the mass is doubled?

the body's situation won't change the forces are equal opposit and on the same body

i think the answer is a, hope this : )

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form