Mathematics
Assertion (A) : The mean of 19 numbers is 38. If the mean of the first 10 numbers is 36 and that of the last 10 is 40, then the 10th number is 38.
Reason (R) : Mean =
A is true, R is false
A is false, R is true
Both A and R are true
Both A and R are false
Statistics
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Answer
Given,
Mean of 19 number = 38
⇒ Total sum = 19 × 38 = 722
Mean of first 10 numbers = 36
⇒ Total sum = 10 × 36 = 360
Mean of last 10 numbers = 40
⇒ Total sum = 10 × 40 = 400
The 10th number is included in both groups:
⇒ First 10 numbers → includes 10th
⇒ Last 10 numbers → also includes 10th
So,
⇒ 10th number = (Sum of first 10 numbers + Sum of last 10 numbers)- Sum of all the 19 numbers
= (360 + 400) - 722
= 760 - 722 = 38.
∴ Assertion (A) is true.
We know that,
Mean =
∴ Reason (R) is true.
Both Assertion (A) and Reason (R) are true.
Hence, option 3 is the correct option.
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Related Questions
The runs scored by a cricketer in last 20 innings are given below.
32 17 0 61 17 32 5 17 70 61 5 17 32 61 5 17 32 70 32 17 The mean runs of the cricketer per inning is :
21
24
29
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Case Study:
A school organized a Health Check Up Camp for its students. The weights (in kg) of the students of a class were recorded as below :41, 40, 36, 52, 50, 48, 47, 45,
40, 41, 42, 49, 50, 51, 38, 41,
40, 45, 40, 39, 49, 51, 48, 46,
44, 50, 57, 38, 41, 51Based on the above information, answer the following questions:
The range of the data is :
(a) 20 kg
(b) 21 kg
(c) 22 kg
(d) 23 kgMean weight of the data is :
(a) 45 kg
(b) 44.5 kg
(c) 42.5 kg
(d) 40.5 kgMedian of the data is :
(a) 44 kg
(b) 45 kg
(c) 45.5 kg
(d) 46 kgOne student weighing 45 kg, was absent on that day. Next day, the teacher added his name in the list. The average weight of the new group is :
(a) 47 kg
(b) 46.4 kg
(c) 46 kg
(d) 45 kgThe median weight of the students after adding the absentee in the list is :
(a) 45 kg
(b) 46 kg
(c) 44.5 kg
(d) 44.2 kg
Assertion (A) : The mean of 15 observations was found to be 21. Later it was detected that one value 15 was wrongly copied as 18, while calculating the mean. The correct mean is 20.
Reason (R) : The mean of n observations x1, x2, x3, ….., xn is . If each observation is increased by p, then the new mean is increased by p, i.e., the new mean is + p.
A is true, R is false
A is false, R is true
Both A and R are true
Both A and R are false
Which of the following statements is/are correct?
(i) Mean of a data can be smaller than the smallest number of the data.
(ii) Mean of a data can be bigger than the largest number of the data.
Only (i)
Only (ii)
Both (i) and (ii)
Both are wrong