Answer:
False
Step-by-step explanation:
Earth is divided into three parts, namely-
a) Crust
b) Mantle
c) Core
The core, including the inner and the outer core, starts from the depth of about 2900 km up to 6400km. It is a depth greater than the depth from the surface of the earth to the lower limit of the mantle. It is comprised of the denser materials here, where the outer core is liquid and the inner core is solid. The density is maximum here. Since density and mass are directly proportional, so it can be considered that the mass also is significantly high in this region. It covers more than about 50% of the earth's total mass.
Thus it does not form one-third of the earth's mass.
hence, the above-given statement is false.