Find the probability that three numbers chosen at random from first nine natural numbers from an A.P.

Find the mean of first ten natural numbers

Find the variance of first n natural numbers.

Find the probability that an even integer chosen at random from first 400 positive integers is divisible by 5 or 7?

Find the average of first n-natural numbers.

Find the median of first n-natural numbers.

A natural number is chosen at random from the first 100 natural numbers. The probability that x+(100)/x > 50 is 1//10 b. 11//50 c. 11//20 d. none of these

Four digit number are formed by using the digits 1,2,3,4 and 5 wihout repeating any digit.Find the probability that a number chosen at random is an odd number.

Three numbers are chosen at random from the first 20 natural numbers. The probability that their product is even is -

Find the probability that a randomly chosen three-digit number has exactly three factors.