Question
There are three numbers 'p', 'q' and 'r' such that average
of 'p' and 'q' is 12, average of 'q' and 'r' is 28 and average of 'p' and 'r' is 20. Find the average of 'p', 'q' and 'r'.Solution
p + q = 2 × 12
Or, p + q = 24 -------- (I)
q + r = 2 × 28
Or, q + r = 56 -------- (II)
p + r = 2 × 20
Or, p + r = 40 -------- (III)
On adding equations I, II and III,
We get, p + q + q + r + p + r = 24 + 56 + 40
Or, 2 × (p + q + r) = 120
Or, p + q + r = 60
Therefore, required average = (60/3) = 20
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