Time And Work Model Questions & Answers, Practice Test for ssc chsl tier 1 2023

Question :1

A boy rows a boat against a stream flowing at 2 kmph for a distance of 9 km, and then turns round and rows back with the current. If the whole trip occupies 6 hours, find the boy's rowing speed in still water.

Answer: (a)

Let the speed of rowing be x. Then the equation formed

is $9/{x - 2} + 9/{x + 2}$ = 6.

${9(x + 2 + x - 2)}/{x^2 - 4}$ = 6

⇒18x = 6($x^2$ – 4)

⇒$x^2$ – 3x – 4 = 0

⇒(x – 4) (x + 1) = 0

x = 4, –1

Speed of rowing 4 km/h

Question :2

150 metres long train crosses a bridge of length 250 metres in 30 seconds. Find the time for train to cross a platform of 130 metres.

Answer: (a)

Speed of train = ${150 + 250}/{30} = {400}/{30} = {40}/3$ m/s

∴ Required time = ${150 + 130}/{40/3} = {280 × 3}/{40}$ = 21 sec

Question :3

'A' can complete a piece of work in 12 days. 'A' and 'B' together can complete the same piece of work in 8 days. In how many days can 'B' alone complete the same piece of work?

Answer: (b)

Number of days = ${12×8}/{12-8}$

= 24 days

Question :4

A garrison had provision for a certain number of days. After 10 days, $1/5$ of the men desert and it is found that the provisions will now last just as long as before. How long was that ?

Answer: (d)

Initially, let there be x men having food for y days.

After 10 days, x men had food for (y – 10) days. Also,

$(x - x/5)$ men had food for y days.

∴ x(y –10) = ${4x}/5$ × y⇒5xy– 50x = 4xy⇒xy– 50x = 0

⇒ x(y – 50) = 0⇒y – 50 = 0⇒y = 50.

Question :5

Two persons living in different towns 32 km apart started at 1 pm to see each other at the rate of 3.5 km/h and 4.5 km/h respectively. When will they meet and how many km will each then walk ?

Answer: (d)

Relative speed = (3.5 + 4.5) = 8 kmph.

Time to meet = 32/8 = 4 hours.

So when they meet at 5 pm, one will have walked

3.5 × 4 = 14 km and the other will have walked

4.5 × 4 = 18 km.

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