Jenna has a bag that contains 7 red marbles and 25 blue marbles. she selects a marble at random, and then, without replacing the first one, selects another marble at random.

what is the probability that jenna selects a blue marble and then a red marble? round your answer to the nearest percent.

p(blue and red) ≈

Jenna has a bag that contains the following
 => 7 red marbles
=> 25 blue marbles.
She selects a marble at random, and then, without replacing the first one, selects another marble at random.
=> 7 + 25 = 32 marbles are there in all.
For blue marble 
=> 1/32 is the probability
For red 
=> 1/31 is the probability
or 
3%

So if we have a total of 32 marbles in the bag and the first pull we want a blue we can say the total number of favorable outcomes is 25/32 then to pull a red marble is 7/31 because one marble had been removed. 

25/32 x 7/31 = 0.176 So now we need to round to the nearest percent which would be 18% chance.

She should use 12/3 to measure

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.