Suppose that an experiment is repeated four times. A certain event has probability 1/10 in a single repetition of the experiment. What is the probability that it occurs in the fourth trial only?

a. 1/4
b. 9/10,000
c. 729/10,000

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.

Can someone show me step by step how to do this?