In a class room the ratio of number of
girls to that of boys is 3:4. The
average height of students in the class
is 4.6 feet. If the average height of the
boys in the class is 4-8 feet, then what
is the average height of the girls in the
class ?
(a) Less than 4.2 feet
(b)More than 4.2 feet but less than
4.3 feet
(c) More than 4.3 feet but less than
4.4 feet
(d) More than 4.4 feet but less than
4.5 feet
Answers
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Answer:
there are 14 boys in the class and they average 5.3 feet, then the total height of the 14 boys is:
14
×
5.3
f
e
e
t
=
74.2
f
e
e
t
With a new boy admitted to the class there are now 15 boys and they average 5.25 feet, then the new total height of the 15 boys is:
15
×
5.25
f
e
e
t
=
78.75
f
e
e
t
To find the height of the new boy we subtract the old total height of all the boys (74.2 feet) from the new total height of all the boys (78.75 feet):
78.75
f
e
e
t
−
74.2
f
e
e
t
=
4.55
f
e
e
t
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