RRB NTPC - Time and Work :(96) MCQs with Answers

1.

A and B working together can complete a work in 12 days, B and C working together will complete the work in 15 days, C and A working together can complete the work in 20 days. If all three work together, in how many days the work can be completed?

   A.) 10 days
   B.) 8 days
   C.) 13 days
   D.) 12 days

Answer: Option 'A'

Given
A + B 's one day work will be 1/12
Similarly, B + C's one day work will be 1/15
C + A 's one day work be 1/20
A + B = 1/12 ----> (1)
B + C = 1/15 ----> (2)
C + A = 1/20 ----> (3)
Adding all the above equation we get
2(A+B+C) = 1/12 + 1/15 + 1/20
=> 5/60 + 4/60 + 3/60
=> 12/60
A+B+C = 12 / 120
= 1/10
If all three work together, the work will be completed in 10 days.

2.

A can finish a work in 18 days and B can do the same work in half the time taken by A. Then, working together, what part of the same work they can finish in a day? 

   A.) 1/6
   B.) 1/9
   C.) 2/5
   D.) 2/7

Answer: Option 'A'

B alone can do the same work in 9 days 
So, the No. of days both of them together take to do the work = 18 × 9/ 18 + 9 
=18 × 9/27 = 6 days. 
The part of the work, they together finish in one day = 1/6.

3.

Three men, four women and six children can complete a work in 7 days . A woman does double the work a man does and a child does half the work a man does. How many women can complete this work in 7 days? 

   A.) 8
   B.) 7
   C.) 12
   D.) 14

Answer: Option 'B'

3 men = 3/2 women 
1 child = 1/2/2 = ¼ woman 
Then, 6 children = ¼ × 6 = 6/4 = 3/2 women 
Then, 3/2 women + 4 women + 3/2 women = 7 women
7 women does the work in 7 days. 
Therefore, the No. of women required to finish the work in 7days = 7.

4.

A can do a work in 4 days, B can do it in 5 days and C can do it in 10 days. A, B and C together can do the work in 

   A.) 1 3/5 days
   B.) 1 9/11 days
   C.) 2 5/6 days
   D.) 3 days

Answer: Option 'B'

When A, B and C can do a work in x, y and z days respectively. Then, the three of them 
together can finish the work in xyz/ x y + y z + x z days 
That is, A, B and C together ca do the work in 4 × 5 × 10/ 20 + 50 + 40 
= 4 × 5 × 10/110 = 20/11 = 1 9/11 days.

5.

Six men or tern boys can do a piece of work in fifteen days. How long would it take for 12 men and 5 boys to do the same piece of work? 

   A.) 6 days
   B.) 28 days
   C.) 25 days
   D.) 7 days

Answer: Option 'A'

6 men = 10 boys 
Then, 1 boy = 6/10 men = 3/5 men 
Then, 5 boys = 3/5 × 5 = 3 men 
12 men + 5 boys = 15 men 
1 work done = 6 men × 15 days 
Therefore, 6 × 15 = 15 × ? days 
? days = 6 × 15/15 = 6 days.

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