SSC CGL Model Paper 11

Question : 68 of 100

Marks: +1, -0

A journey of 144 km takes one hour less by a fast train (A) than by a slow train (B). if the average speed of B is 24 km/h less than that of A, then the average speed (in km/h) of A is ?

36km/h
48 km /h
46 km /h
72 km/h

Validate

Solution:

D = 144km
Let

t _1= x, t_ 2 = x + 1

s_1 = y, s_2 = y -24

xy = (x+1) (y-24)

xy = xy - 24x +y -24

24x - y = -24

xy=144

y=144/x

24x-144/x=-24

x^2+x-6=0

x(x+3)-2(x+3)=0

(x+3) (x-2)=0

x=2

∴y=72

speed of A = 72 km /h

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