If the letters a b c d e and f are to be used in a five letter code how many different codes are possible if reperirions are not permitted

Describe in detail how you would construct a 95% confidence interval for a set of 30 data points whose mean is 20 and population standard deviation is 3. be sure to show that you know the formula and how to plug into it. also, clearly state the margin of error.

Ammonia molecules have three hydrogen atoms and one nitrogen atom.how many of each atom arein five molecules of ammonia

Write the pair of fractions as a pair of fractions with a common denominator