Question

The average of five numbers is 100. If the average of first three is 80 and that of last three is 120, the third number is :

Answer 1

the last number is 100

Answer 2

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Average =$\frac{Sum \:of\: observations}{No. \:of \: observations}$

Sum of 5 numbers = 100×5
=500

Sum of First three numbers=80×3
=240

Sum of Last three numbers =120×3
=360

Third number =(360+240)-500
=600-500
=100



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