Learn UNIT VII: Statistics and probability with Free Lessons & Tips

First 10 Natural numbers are:- 1,2,3,4,5,6,7,8,9,10

Mean = Sum of all numbers/ total number of observations

        = 1+2+3+4+5+6+7+8+9+10 / 10 

        = 55/ 10 

        = 5.5

Therefore, 5.5 is the mean of first 10 natural numbers

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6.If the mean of 4 numbers, 2,6,7 and a is 15 and also the mean of other 5 numbers, 6, 18, 1, a, b is 50. What is the value of b? read less

in this question mean is already given and we know that:-

           mean = sum of total numbers / total number of observations

             15 = 2+6+7+a / 4

             15*4 = 15+a

               60 = 15+a

               60-15 = a

                 a= 45

now we have found the value of a=45, we will put this value in second series:-

                mean = sum of all numbers / total number of observations

                50 = 6+18+1+45(value of a) + b / 5

                50*5 = 70 + b

                250 = 70 + b

                 b = 250 - 70

                 b = 180

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1. Cards each marked with one of the numbers 6, 7, 8, ....., 15 and placed in a box and mixed throughly. One card is drawn at random from the box. What is the probability of getting a card with number less than 10? read less

9. Cards bearing numbers 3 to 20 are placed in a bag and mixed thoroughly. A card is taken out from the bag at random. What is the probability that the number on the card taken out is an even number? read less

1. In a continuous frequency distribution, the median of the data is 21. If each observation is increased by 5, then find the new median. read less

2. The average score of boys in the examination of a school is 71 and that of the girls is 73. The average score of the school in the examination is 71.8. Find the ratio of the number of boys to the number of girls who appeared in the examination. read less