# Tutoring math, you see all kinds of scientific calculators. The tutor continues to praise the Casio fx-991ES PLUS C.

If you were to be marooned on an island with a single calculator…which one would you prefer? The question is absurd, of course. Yet, I believe I know my answer: the Casio fx-991ES PLUS C. It has seemingly endless functionality for a little scientific calculator.

Today I noticed that it calculates binomial pdf.

**Example: Using the Casio fx-991ES PLUS C, find the probability of 20 successes in 35 trials when p=0.44.**

Solution:

- Press MODE, then arrow down
- Select 3
- Select 4
- For a single query, select 2
- It will ask for x (the number of successes). Key in 20 =
- Next, it will ask for N (the number of trials). Key in 35 =
- Now it will ask for p (the probability of success each time). Key in .44 =
- Hopefully you receive the answer 0.0401

HTH:)

Source:

*Casio fx-991ES PLUS C User’s Guide*

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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