Vimla starts for office every day at 9 am and reaches exactly on time if she drives atĀ her usual speed of 40 km/hr. She is late by 6 minutes if she drives at 35 km/hr. OneĀ day, she covers two-thirds of her distance to office in one-thirds of her usual total time toĀ reach office, and then stops for 8 minutes. The speed, in km/hr, at which she shouldĀ drive the remaining distance to reach office exactly on time is
Let distance = d
Given,Ā $$\frac{d}{35}-\frac{d}{40}=\frac{6}{60}$$
=> d = 28km
The actual timeĀ taken to travelĀ 28km = 28/40 = 7/10 hours = 42 min.
Given time taken to travel 58/3 km = 1/3 *42 = 14 min.
Then a break of 8 min.
To reach on time, he should cover remaining 28/3 km in 20 min => Speed =Ā $$\frac{\left(\frac{28}{3}\right)}{\frac{20}{60}}=28\ $$ km/hr
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