An express train takes 30 minutes less for a journey of 440 km, if it's usual speed is increased by 8km/hr. Find its usual speed
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2
Answer:
Let the speed of the car be
s
and time be
t
Then,
s
t
=
440
⟹
s
=
440
t
and
(
s
+
8
)
(
t
−
1
2
)
=
440
(
440
t
+
8
)
(
2
t
−
1
)
=
880
(
8
t
+
440
)
(
2
t
−
1
)
=
880
t
16
t
2
−
8
t
+
880
t
−
440
=
880
t
16
t
2
−
8
t
−
440
=
0
2
t
2
−
t
−
55
=
0
2
t
2
−
11
t
+
10
t
−
55
=
0
(
2
t
−
11
)
(
t
+
5
)
=
0
t
=
5.5
,
−
5
Hence time is
5.5
hr
Speed
=
440
5.5
=
80
k
m
/
h
r
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