Earth's diameter = 12,742 km
Earth's radius = 6,371 km
Earth's volume = 6,371 × 6,371 × 6,371 × 4/3 π (assuming Earth is spherical)
= (1.083206917 × 1012) km3
Volume of water in Earth (assuming percentage of water in Earth = 71%)
= (7.69076911 × 1011 ) km3
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Earth's surface area = 4π × 6,371 × 6,371
= (5.100644719 × 108 )km2
Surface area of water in Earth (assuming percentage of water in Earth = 71%)
= (3.621457751 × 108) km2
I'm not sure if my statement is correct.