1.

The mean of 35 observations is 20, out of which mean of first 18 observations is 15and mean of last 18 observation is 25. Find the 1 8th observation.)

Answer»

Mean=Sum/n

Mean of 35 observation=Sum/3520=Sum/35sum=35*20=700

Mean of first 18 observation=S1/15=S1/18S1=15*18=270

Mean of last 18 observation=S2+18th term/1825=S2/18S2=25*18=450

Sum-270=450-18th term700-270-450=-18th term18th term=720-700=20



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