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Question 31: 1 have to be at a certain place at a certain time and find that I shall be 40 minutes late, if I walk at the rate of 4 kmph and 40 min early if I walk at the rate of 5 kmph. What is the usual time required by me to reach my destination? [1] 7 hrs [2] 14 hrs [3] 6 hrs [4] 3.5 hrs

Question 32: Two men A and B walk from P to Q, a distance of 21 km, at 3 and 4 km an hour respectively. B reaches Q, returns immediately and meets A at R. The distance from P to R is [1] 12 km [2] 18 km [3] 10 km [4] 24 km

Answer:

Option: 2

Explanation:

When B meets A at R, B has walked the distance PQ + QR and A the distance PR.

That is, both of them have together walked twice the distance from P to Q, i.e. 42 km.

Now, the speed of A and B are in the ratio 3 : 4, and they have walked 42 km.

Hence, the distance PR travelled by A = 3/7 of 42 km = 18 km.

Question 33: A person can row at the rate of 3 kmph in still water. If the river is running at 1.2 kmph, then it takes him 2 hours to row to a place and back. How far is the place? [1] 5 km [2] 2.5 km [3] 6 km [4] 8 km

Answer:

Option: 2

Explanation:

X = 3 kmph, Y = 1.2 kmph. Since time taken = Distance/Speed = 2 hrs.

=> D/4.2 + D/1.8 = 2 =>(1.8 D + 4.2 D)(4.2 x 1.8).

=> D = 2.52 km.

Question 34: The current of a stream runs at 5 kmph. A motor launch goes 25 km upstream and back again to the starting point in 275/2 minutes. The speed of the motor launch in the absence of any current is [1] 22.8 kmph [2] 10.1 kmph [3] 31.6 kmph [4] 6 kmph

Answer:

Option: 1

Explanation:

Let X = Speed of motor launch.

Y = Speed of current = 5 kmph. Distance = 25 km.

Time required = 275/(2 x 60) hrs = 25/(X + 5) +25/(X — 5).

Neglect the negative sign => X= 105/4.6 = 22.82 kmph.

Question 35: A man can row with the stream at the rate of 20 kmph and against the stream at 5 kmph. The man's rate in still water is [1] 7.5 kmph [2] 12.5 kmph [3] 17.5 kmph [4] 15.5 kmph