4
Q:

# A person can row 8 1/2 km an hour in still water and he finds that it takes him twice as long to row up as to row down the river. The speed of the stream ?

 A) 1.78 kmph B) 2.35 kmph C) 2.83 kmph D) 3.15 kmph

Explanation:

Given speed of the person = 8 1/2 = 17/2 kmph
Let the speed of the stream = x kmph
speed of upstream = 17/2 - x
speed of downstream = 17/2 + x
But given that,
2(17/2 - x) = 17/2 + x
=> 3x = 17/2
=> x = 2.83 kmph.

Q:

Karthik could cover a distance of 200 km in 22 days while resting for 2 hrs. per day. In how many days (approx) he will cover a distance of 250 km while resting for 2 hrs. per day and moving with 2/3rd of the previous speed ?

 A) 41.25 days B) 37.5 days C) 39.75 days D) 40 days

Explanation:

Given Karthik can cover the distance of 200 kms resting 2 hrs per day in 22 days.

Let the initial speed be '1'

Hence, Time = 22(24hrs - 2)

Noe new speed = 2/3

Let the number of days he take be 'D'

Therefore, $\inline \fn_jvn \small \frac{22(24-2)x3}{200}=\frac{D(24-2)x2}{250}$

D = 11 x 3 x 5/4 = 41.25 days. = 41 1/4 days.

7 118
Q:

A bus covers its journey at the speed of 80km/hr in 10hours. If the same distance is to be covered in 4 hours, by how much the speed of bus will have to increase ?

 A) 85 km/hr B) 95 km/hr C) 105 km/hr D) 120 km/hr

Explanation:

Initial speed = 80km/hr
Total distance = 80 x 10 = 800km
New speed = 800/4 =200km/hr
Increase in speed = 200 - 80 = 120km/hr

6 172
Q:

Joel travels the first 3 hours of his journey at 60 mph speed and the remaining 5 hours at 24 mph speed. What is the average speed of Joel's travel in kmph ?

 A) 38 kmph B) 40 kmph C) 60 kmph D) 54 kmph

Explanation:

Average speed = Total distance / Total time.

Total distance traveled by Joel = Distance covered in the first 3 hours + Distance covered in the next 5 hours.

Distance covered in the first 3 hours = 3 x 60 = 180 miles
Distance covered in the next 5 hours = 5 x 24 = 120 miles

Therefore, total distance traveled = 180 + 120 = 300 miles.

Total time taken = 3 + 5 = 8 hours.

Average speed = 300/8 = 37.5 mph.

we know that 1 mile = 1.6 kms

=> 37.5 miles = 37.5 x 1.6 = 60 kms

Average speed in Kmph = 60 kmph.

2 158
Q:

Two persons start running simultaneously around a circular track of length 600 m from the same point at speeds of 25 kmph and 35 kmph. When will they meet for the first time any where on the track  ?

 A) 54 sec B) 36 sec C) 72 sec D) 11 sec

Explanation:

Time taken to meet the first time = length of track/relative speed

Given the length of the track is 600 m

The relative speed = 25 + 35 = 60 kmph = 60 x 5/18 m

Therefore Time = $\inline \fn_jvn \frac{600}{(25+35)\frac{5}{18}}$  = 600/60 x (18/5) = 36 sec.

2 167
Q:

A boy can swim in still water at 4.5 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is ?

 A) 1.8 kmph B) 2 kmph C) 2.2 kmph D) 1.5 kmph

Explanation:

Speed of Boy is B = 4.5 kmph

Let the speed of the stream is S = x kmph

Then speed in Down Stream = 4.5 + x

speed in Up Stream = 4.5 - x

As the distance is same,

=> 4.5 + x = (4.5 - x)2

=> 4.5 + x = 9 -2x

3x = 4.5

x = 1.5 kmph