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Answers
here is your answer of the second question
there is four images
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Answer:
ANSWER 1.
Let x= Original Speed
we know that
speed
distance
=time
So as per the question the following equation can be formed
x
360
−
x+5
360
=
60
48
[1 hour = 60 minutes]
⇒
x
1
−
x+5
1
=
60
48
⋅
360
1
⇒
x
2
+5x
5
=
450
1
⇒x
2
+5x−2250=0
⇒x
2
−45x+50x−2250=0
⇒x(x−45)+50(x−45)=0
⇒(x−45)(x+50)=0
x=45,−50
As the speed can't be negative so,
x=45
ANSWER 2
Let the speed of the boat in still water be x km/h and speed of the stream is y km/h.
Therefore, speed of the boat while upstream is (x−y) km/h and speed of the boat while downstream is (x+y) km/h
As we know that speed=
time
distance
, therefore, time=
speed
distance
It is given that the motor boat can travel 30 km upstream and 28 km downstream in 7 hours and also it can travel 21 km upstream and return in 5 hours, thus,
x+y
30
+
x−y
28
=7.............(1)
x+y
21
+
x−y
21
=5.............(2)
Let
x+y
1
=u and
x−y
1
=v, then the equations (1) and (2) becomes:
30u+28v=7..........(3)
21u+21v=5..........(4)
Multiplying equation (3) by 21 and equation (4) by 30 we get,
630u+588v=147..........(5)
630u+630v=150..........(6)
Now subtracting equation (5) from equation (6), we get
42v=3
⇒v=
14
1
Substitute the value of v in equation (4) then, u=
6
1
Since
x+y
1
=u and
x−y
1
=v, therefore,
x+y=6..........(7)
x−y=14..........(8)
Adding equations (7) and (8), we get:
2x=20
⇒x=10
Hence, the speed of the boat in still water is 10 km/h.
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