mean of 6 numbers is is 50. the mean of last four numbers is 40 and first three is 70. then the four the number is
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The average of 7 numbers is 50. The average of the first three is 40, while the average of the last three is 60. What must be the remaining number?
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C. S. Sharma
Answered April 1, 2019
Imagine that seven numbers are a, b, c, d, e, f and g . The average of these 7 numbers is 50. As such
Sum of these numbers will be
a+b+c+d+e+f+g
Average = sum of the numbers/ n
Accordingly (a+b+c+d+e+f+g)/7=50
(a+b+c+d+e+f+g)=50×7
(a+b+c+d+e+f+g)=350…Eq.1
As per the statement, the average of first three numbers is 40, means
(a+b+c)/3=40
(a+b+c)=40×3
(a+b+c)=120…Eq. 2
Further, the statement suggest the average of last three numbers is 60
(e+f+g)/3=60
(e+f+g)=60×3
(e+f+g)=180…Eq.3
Substitute the value of (a+b+c) from Eq. 2 and the value of (e+f+g) from Eq. 3 into the Eq. 1
(a+b+c+d+e+f+g)=350…Eq.1
(a+b+c)+d+(e+f+g)=350
120+d+180=350
d+300=350
d=350–300
d=50
Thus the value of remaining number d is 50
Answer the value of remaining number is 50