1. a jar contains 100 marbles total. some are black. if you pull 4 marbles out and 1 is black
how many out of the 100 marbles would you guess are black?

The number of black marbles in a jar containing 100 marbles  is ;  25 black marbles

Given that:

Jar contains 100 marbles

out of every 4 marbles pulled, 1 marble  = black

∴ probability of picking a black marble = 1/4

Determining the number of black marbles contained in 100 marbles

= 1/4 * Total number of marbles

= 1/4 * 100 marbles =  25 black  marbles

Hence we can conclude that the number of black marbles in a jar  containing 100 marbles = 25 black marbles

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