Question

In a class of 5 students, average weight of the 4 lightest students is 40 kgs.
Average weight of the 4 heaviest students is 45 kgs. What is the difference
between the the maximum and minimum possible average weight overall?
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Answer 1

Answer:

Since the total weight of the 4 lightest students is 4 x 40 = 160 kg, we have a + b + c + d = 160. Similarly, since the total weight of the 4 heaviest students is 4 x 45 = 180 kg, we have b + c + d + e = 180.