In a lot of 12 microwave ovens, there are 3 defective units. A person has ordered 4 of these units and since each is identically packed. What is the probability that : exactly 3 units are good.

In a lot of 12 microwave ovens, there are 3 defective units. A person has ordered 4 of these units and since each is identically packed. What is the probability that : all units are good.

On one page of a telephone directory, there were 200 telephone numbers. The frequency distribution of their unit place digit (for example, in the number 25828573, the unit place digit is 3) is given in Table 15.7 : Without looking at the page, the pencil is placed on one of these numbers, i.e., the number is chosen at random. What is the probability that the digit in its unit place is 6?

Four persons are selected at random out of 3 men, 2 women and 4 children. The probability that there are exactly 2 children in the selection is:

From a lot of 10 items containing 3 defective items a sample of 4 items is drawn at random. Let the random variable 'X' denote the number of defective items in the sample. If the sample is drawn without replacement, find: the probability distribution of X.

Silver crystallises with face centred cubic unit cells. Each side of the unit cell has a length of 409 pm. What is the radius of an atom of silver ? (Assu!'le that each face atom is touching the four corner atoms)

If the lengths of the side of a triangle are 3,4 and 5 units, then find the circum radius R.

A conductor of capacity 4 units, charged with 100 units of positive charge is connected to another conductor of capacity 2 units, charged with 20 units of negative charge. What is the change in potential of each conductor ? What will be the charges of each of them after connection?

If P(-1,2) and Q(3,-7) are two points, express the vector PQ in terms of unit vectors hati and hatj also, find distance between point P and Q . What is the unit vector in the direction of PQ ?