How to do an Average
Formula for doing an Average : [ Sum of observations / Number of observation ]
Ex:1: There are 36 students in a mess. Due to admission of 6 new students, the expenditure of the mess were increased by Rs 42 per day while the average expenditure per head diminished by Rs 2. What could be the original expenditure of the mess.
Solution: Consider the original average expenditure be Rs 'x'.
==> 42(x-2)-36x = 42
==> 6x-84 = 42
==> 6x = 42+84 = 126
==> x = 21
:: Original expenditure is ==> 36x21 = Rs 756
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