Aptitude ➤ Averages ➤ Set 1

#### Averages : Important Facts and Formulae

Average:
Average = Sum of observations / Number of observations

Average Speed :
Suppose a man covers a certain distance at x kmph and an equal distance at y kmph.
Then, the average speed druing the whole journey is [2xy/(x+y)] kmph.
Question 36
Q36.  A student find the average of 10, 2-digit numbers. If the digits of one of the numbers is interchanged, the average increases by 3.6. The difference between the digits of the 2-digit numbers is
Question 37
Q37.  The average (arithmetic mean) of 330, 360 and 390 is :
Question 38
Q38.  In a team of 10 persons, nine persons spent Rs. 40 each for their meal and the remaining one spent Rs. 9 more than the average expenditure of all the 10 persons. Tho total expenditure for their meal was :
Question 39
Q39.  In an examination average marks obtained by the girls of a class is 85 and the average marks obtained by the boys of the same class is 87. If the girls and boys are in the ratio 4 : 5, average marks of the whole class (approximately) is closest to :