Question

By walking at 3/4 of his usual speed, a man reaches his office 20 minutes later than usual . his usual time is :

Answer 1

Let his usual speed be x
Let his usual time be y
Let distance be z
z=x×y
z=((3/4)x)×(y+20)
x×y=(3x/4)×(y+20)
x/(3x/4)=(y+20)/y
4/3=1+(20/y)
(4/3)-1=(20/y)
1=20/y
y=20min
His usual time = 20min

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