Question

the mean of the 5 smallest number from a group is 15 while the mean of all the 13 members of the group taken together is 17.what is the mean of the 8 largest numbers?​

Answer 1

Consider all 13 numbers as a, b, c, d, e, f, g, h, l, m

Mean of 5 smallest numbers = 15

Sum of numbers/Number of numbers = 15

(a + b + c + d + e)/5 = 15

a + b + c + d + e = 15 * 5

a + b + c + d + e = 75 ---- (1)

Mean of all 13 numbers = 17

Sum of numbers/Number of numbers = 17

(a + b + c + d + e + f + g + h + i + j + k + l + m)/13 = 17

a + b + c + d + e + f + g + h + i + j + k + l + m = 17 * 13

a + b + c + d + e + f + g + h + i + j + k + l + m = 221

(a + b + c + d + e) + f + g + h + i + j + k + l + m = 221

75 + f + g + h + i + j + k + l + m = 221

f + g + h + i + j + k + l + m = 221 - 75

f + g + h + i + j + k + l + m = 146

So, Sum of 8 largest numbers = 146

Mean of 8 largest numbers = Sum of numbers/ Number of numbers

= 146/8

Mean of 8 largest numbers = 18.25