18. The figure shows two iron nails X and Y
hanging from a magnet. Which of the following
statements is incorrect?
A. Top of nail Y is north pole and bottom
of nail Y is south pole.
B. Top of nail X is north pole and bottom
of nail X is south pole.
Magnetic properties are induced into both
the nails X and Y.
D.
Magnetic properties are induced into the nail X only.
Y
please help with the answer
Answers
Answer:
Speed of train = 60 km/hr
Speed of car = 80 km/hr
Step-by-step explanation:
Given:
A man travels 300 km partly by train and partly by car
He takes 4 hours if he travels 60 km by train and rest by car.
If he travels 100 km by train and rest by car he takes 10 minutes longer
To Find:
Speed of train
Speed of car
Solution:
Let the speed of the train be a km/hr and speed of the car be b km/hr.
By first case given,
Distance travelled by train = 60 km
Distance travelled by car = (300 - 60) = 240 km
Time taken = 4 hours
We know that,
Time = Distance/Speed
Hence,
\sf \dfrac{60}{a} +\dfrac{240}{b} =4---(1)
a
60
+
b
240
=4−−−(1)
By the second case given,
Distance travelled by train = 100 km
Distance travelled by car = (300 - 100) = 200 km
Time taken = 4 hours + 10 mins = (4 + 10/60) hours = 25/6 hours
Therefore,
\sf \dfrac{100}{a} +\dfrac{200}{b} =\dfrac{25}{6} ---(2)
a
100
+
b
200
=
6
25
−−−(2)
Now let 1/a = x and 1/b = y
Hence equation 1 and 2 changes to
60 x + 240 y = 4 -----(3)
100 x + 200 y = 25/6---(4)
Multiply equation 3 by 5 and equation 4 by 3
Hence,
300 x + 1200 y = 20
300 x + 600 y = 25/2
Solving the above equations by elimination method,
600 y = 15/2
y = 15/1200
y = 1/80
Substitute the value of y in equation 3,
60 x + 3 = 4
60 x = 1
x = 1/60
Now we know that,
1/a = x, 1/x = a and 1/b =y, 1/y = b
Hence,
a = 60 km/hr = Speed of the train
b = 80 km/hr = Speed of the car
Hence the speed of the train is 60 km/hr and speed of the car is 80 km/hr.