Ques. A man can row at 5 kmph in still water. If the velocity of the current is 1 kmph and it takes him 1 hour to row to a place and come back. how far is that place.

.4 km

1.4 km

2.4 km

3.4 km

Answer And Explanation

Answer: Option C

Explanation:

Let the distance is x km

Rate downstream = 5 + 1 = 6 kmph

Rate upstream = 5 – 1 = 4 kmph

then

x/6 + x/4 = 1 [because distance/speed = time]

=> 2x + 3x = 12

=> x = 12/5 = 2.4 km

Ques. The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is

1.6 km

2 km

3.6 km

4 km

Answer And Explanation

Answer: Option C

Explanation:

Speed downstreams =(15 + 3)kmph

= 18 kmph.

Distance travelled = (18 x 12/60)km

= 3.6km

Ques.Sahil can row 3 km against the stream in 20 minutes and he can return in 18 minutes. What is rate of current ?

1/2 km/hr

1/3 km/hr

2 km/hr

4 km/hr

Answer And Explanation

Answer: Option A

Explanation:

Speed Upstream=

3/(20/60)=9km/hrSpeed

Downstream=3(18/60)=10km/hr

Rate of current will be (10−9)/2

=1/2km/hr

Ques. In how many words can be formed by using all letters of the word BHOPAL

420

520

620

720

Answer And Explanation

Answer: Option D

Explanation:

Required number

=6!=6∗5∗4∗3∗2∗1=720

Ques. In how many way the letter of the word “APPLE” can be arranged

20

40

60

80

Answer And Explanation

Answer: Option C

Explanation:

Friends the main point to note in this question is letter “P” is written twice in the word.

Easy way to solve this type of permutation question is as,

So word APPLE contains 1A, 2P, 1L and 1E

Required number =

=5!/(1!∗2!∗1!∗1!)

=(5∗4∗3∗2!)2!

=60

In how many way the letter of the word “RUMOUR” can be arranged

2520

480

360

180

Answer And Explanation

Answer: Option D

Explanation:

In above word, there are 2 “R” and 2 “U”

So Required number will be

=6!/(2!∗2!)

=6∗5∗4∗3∗2∗1/4

=180