Question: The average of Kanchan,s marks in `7` subjects is `75`.His average in six subject excluding Seciene is `72`.How many marks did he get in Seciene ?
A
`72`
B
`90`
C
`93`
D
None of these
Note: Marks in Seciene
`= (7 xx 75 - 6 xx 72)`
`= 93`
Question: Of the three numbers ,second is twice the fist and is also thrice the third .If the average of the three numbers is `44`, the largest number is:
A
`24`
B
`36`
C
`72`
D
`108`
Note: Let `3rd` number be x.
Then,second number
`= 3x`.
;.First number
`= 3x/2`.
`:. x + 3x + 3x/2`
`= (44 xx 3)`
`or (11x)/2`
`= 44 xx 3`
`or x = 24`.
Largest number = 2nd number
`= 3x = 72`
Question: A man spends Rs `1800` monthly on an average for the first four months and Rs `2000`monthly for the next eight months and saves Rs `5600` a year .His average monthly income is:
A
`Rs 2000`
B
`Rs 2200`
C
`Rs 2400`
D
`Rs 2600`
Note: Total annual income
`= Rs (1800 xx 4 + 2000 xx 8 + 5600)`
`= Rs 28800`.
:. Average monthly income
`Rs ((28800)/12)`
`= Rs 2400`.
Question: The average age of `30`students of a class is `12` years .The average age of a group of `5`of the students is `10`years and that of another group of `5`of them is `14` years . What is the average age of the remaining students ?
A
`8 years`
B
`10 years`
C
`12 years`
D
`14 years`
Note: Total age of `20`students
`= (30 xx 12) - (5 xx 10 + 5 xx 14)`
`= 240 years`
:. Required average
`= (240/20)`
`= 12 years`
Question: A class has two section, in one of which there are `40`students with an average of `14.5` years .The average of the class is `14.2`years .If there be `32`students in the other section ,its average age is :
A
`13.5 years`
B
`13.6 years`
C
`13.7 years`
D
None
Note: Total age of `32`students
`= (72 xx 14.2 - 40 xx 14.5) years`
`= (1022.4 - 580) years`
`= 442.4 years`
:. Required average
`= 442.4/32`
`= 13.825 years`