# Vimal starts for office every day at 9 am and reaches exactly on time if she drives at her usual speed of 40 km/hr. She is late by 6 minutes if she dr

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Vimal starts for office every day at 9 am and reaches exactly on time if she drives at her usual speed of 40 km/hr. She is late by 6 minutes if she drives at 35 km/hr. One day, she coves two-thirds of her distance to the office in one-thirds of her usual time to reach office and then stops for 8 minutes. The speed, in km/hr at which she should drive the remaining distance to reach office exactly on time, is
1. 20
2. 28
3. 26
4. 29

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Correct Answer - Option 2 : 28

Calculation:

We can tabulate the given information as follows:

 Time (in hours) Speed (in km/h) Initially t (assume) 40 Finally t + (6/60) 35

Hence, we obtain the distance as:

40t = 35 × [t + (6/60)]

⇒ 5t = 7/2

⇒ t = 42 minutes

So, the total distance = 40 × (42/60) = 28 km

one-thirds of her usual time = 42/3 = 14 minutes

remaining distance = 28/3 km

To reach the office in the usual time, let the required speed be v km/h

⇒ (14/60) + (8/60) + (28/3v) = 42/60

∴ v = 28 km/h