Question
The average of 13 results is 70. The average of first seven is 65 and that of the last seven is 75, the seventh result is :
Answer: Option A Answer: (a)Seventh observation = 65 × 7 + 7 × 75 – 13 × 70 = 455 + 525 – 910 = 980 – 910 = 70 Aliter : Here, n = 13, x = 70 m =7, y = 65 m = 7, z = 75 Seventh result = m (y + z) – nx = 7 (65 + 75) – 13 × 70 = 7 × (140) – 910 = 980 – 910 = 70
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