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Numerical Ability
Averages
Q. The average age of 30 boys of a class is equal to 14 yrs. When the age of the class teacher is included the average becomes 15 yrs. Find the age of the class teacher.
Option
A 40 yrs
B 42 yrs
C 45 yrs
D 46 yrs
Read Solution (Total 11)
-
- The average age of 30 boys of a class is equal to 14 yrs:
i.e Sum of all boys:30*14
include class teacher:31 candidates in a class
& avg age is:15 yr
i.e. sum of all:31*15(include class teacher)=465
so,the age of the class teacher:465-420=45yr
answer will be 45 yrs(option c)
- 11 years agoHelpfull: Yes(25) No(0)
- avg age of 30 boys in class is 14 yrs
sum of ages of boys =30*14=>420
When the age of the class teacher is included the average becomes 15 yrs
sum of ages of boys=31*15=>465
age of Teacher=465-420=45
so answer is 45 years - 11 years agoHelpfull: Yes(1) No(0)
- ans:45
14=sum of ages of boys/30
sum of ages of boys=420
15=420+x(x is the age of teacher)/31
x=45
- 11 years agoHelpfull: Yes(0) No(0)
- including-excluding
31*15-30*14
45 - 10 years agoHelpfull: Yes(0) No(0)
- 30*14=420
31*16=465
465-420=45 ans c 45 - 10 years agoHelpfull: Yes(0) No(0)
- ans: 45
FORMULA:
new person weight = present average+(Total number of persons+increased weight)
= 14+(31*1)
= 45 - 10 years agoHelpfull: Yes(0) No(0)
- From given problem total age of boys=30*14=420
when teacher was included then total agge=(30+1)*15=465
teacher age is=465-420=45 years
- 10 years agoHelpfull: Yes(0) No(0)
- let the age of class teacher =x
30*14 + x = 15*31
420 + x = 465
x = 465-420 = 45years - 8 years agoHelpfull: Yes(0) No(0)
- 45
31×15-30-14=45 - 8 years agoHelpfull: Yes(0) No(0)
- (30*14+x)/31=15
x=45 - 8 years agoHelpfull: Yes(0) No(1)
- 30*14=420
31*15=465
465-420=45years - 7 years agoHelpfull: Yes(0) No(0)
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