which is the best prediction for the number of times the spinner will land on B if she conducts 400 trials?

Question

Dawn is conducting an experiment with a spinner. The spinner has landed on A 4 times, B 7 times, and C 9 times. Based on Dawn's experiment, which is the best prediction for the number of times the spinner will land on B if she conducts 400 trials?

Answer 1

Dawn spun the spinner 20 times. It landed on B 7 times.

Based on this experiment, the spinner will land on B 140 times.

You set up a proportion.

7/20=B/400

20*20=400 so 20*7=140, or...

cross multiply

20B=7*400

20B=2800

2B=280

B=280/2

B=140

In reality the spinner has the same chance of landing on A as it has for landing on B as it has for landing on C.

In reality the spinner should land on A 400/3=133 times, on B 400/3=133 times and on C 400/3=133 times.

This is theoretically speaking. In an experiment anything can happen. However, the more times you repeat the experiment the more chance of the spinner landing on A the same number of times as landing on B as landing on C.

This is called the law of large numbers. As the number of trials increases, the average of the results should be close to what you would expect to happen, called "the expected value