Later on the maximum marks were increased to 100, and accordingly each Student's score was doubled. Find the variance of the new scores .

Fig. depicts an archery target marked with its five scoring areas from the centre outwards as Gold, Red, Blue, Black and White. The diameter of the region representing Gold score is 21 cm and each of the other bands is 10.5 cm wide. Find the area of each of the five scoring regions.

Consider the marks obtained (out of 100 marks) by 30 students of Class IX of a school: Find the mean of the marks obtained by 30 students of Class IX of a school.

Find the perecentage increase in the area of the triangle if each of its sides is doubled.

If each side of a triangle is doubled, then find the percentage increase in its area.

The variance of 20 observations is 5. If each observation is multiplied by 2, find the new variance of the resulting observations.

In an examination, the maximum marks for each of the three papers are 50. Maximum marks for the fourth paper are 100. Find the number of ways in which the candidate can score 60% marks in aggregate.

Marks obtained by 2500 students are shown in the following table: A student is selected at random. Find the probability that : he scores more than 80% marks.

Marks obtained by 2500 students are shown in the following table: A student is selected at random. Find the probability that : he scores less than 60% marks.

A biased dice is such that P(4)=1/10 and the scores are equality likely.The dice is tossed twice. If X is the number of four shown, find the variance of the random variable X.