Weigh 4.5 ounces, 5.01 ounces, 5.3 ounces 4.75 ounces 4.9 ounces which is the best whole number of estimate of how much all the containers wieigh together

I'd round off all five weights, obtaining {4.5, 5, 5, 5, 5}.  The sum of these five weights is 24.5, which we divide by 5 to obtain the estimate:

24.5
=  4.9.  Round this up to the nearest whole number:  5.  This is "the best         5               whole number estimate of the contents of these 5 containers."
   

Planet earth has a mass of 5.9726x10²⁴ kg.then: 5.9726x10²⁴ kg=100% of the total earth mass.if the water´s mass=5x10-4 % of the total mass, we can solve this problem by the rule of three.5.9726x10²⁴ %*10⁻⁴ %x=(5.9726x10²³ kg)(5*10⁻⁴  %) / 100 %=2.9863x10¹⁹ kganswer:   the mass of the planet´s water would be   2.9863 x 10¹⁹ kg.