Time and Work
- 5 persons can prepare an admission list in 8 days working 7 hours a day. If 2 persons join them so as to complete the work in 4 days, they need to work per day for :
-
View Hint View Answer Discuss in Forum
Using Rule 1,
More persons, less working hours/day
Less days, more working hours/dayPersons 7 : 5 
: : 7 : x Days 4 : 8
where, x is hours/days
∴ 7 × 4 × x = 5 × 8 × 7∴ x = 5 × 8 × 7 = 10 hours 7 × 4 Correct Option: A
Using Rule 1,
More persons, less working hours/day
Less days, more working hours/dayPersons 7 : 5 : : 7 : x Days 4 : 8
where, x is hours/days
∴ 7 × 4 × x = 5 × 8 × 7∴ x = 5 × 8 × 7 = 10 hours 7 × 4
- If A, B and C can complete a work in 6 days. If A can work twice faster than B and thrice faster than C, then the number of days C alone can complete the work is :
-
View Hint View Answer Discuss in Forum
Using Rule 3,
Let time taken by A = x days
∴ Time taken by B = 2x days
Time taken by C = 3x days
According to the question,⇒ 1 + 1 + 1 = 1 x 2x 3x 6 ⇒ 6 + 3 + 2 = 1 6x 6 ⇒ 11 = 1 6x 6
⇒ 6x = 6 × 11⇒ x = 6 × 11 = 11 6
∴ Time taken by C alone = 3x
= 3 × 11 = 33 daysCorrect Option: A
Using Rule 3,
Let time taken by A = x days
∴ Time taken by B = 2x days
Time taken by C = 3x days
According to the question,⇒ 1 + 1 + 1 = 1 x 2x 3x 6 ⇒ 6 + 3 + 2 = 1 6x 6 ⇒ 11 = 1 6x 6
⇒ 6x = 6 × 11⇒ x = 6 × 11 = 11 6
∴ Time taken by C alone = 3x
= 3 × 11 = 33 days
- A is twice as good as B and together they finish a piece of work in 16 days. The number of days taken by A alone to finish the work is
-
View Hint View Answer Discuss in Forum
A is twice as good as B.
∴ Time taken by A = x days
Time taken by B = 2x days
According to the question,1 + 1 = 1 x 2x 16 ⇒ 2 + 1 = 1 2x 16 ⇒ 3 = 1 2x 16
⇒ x = 3 × 8 = 24 daysCorrect Option: D
A is twice as good as B.
∴ Time taken by A = x days
Time taken by B = 2x days
According to the question,1 + 1 = 1 x 2x 16 ⇒ 2 + 1 = 1 2x 16 ⇒ 3 = 1 2x 16
⇒ x = 3 × 8 = 24 days
- A man does double the work done by a boy in the same time. The number of days that 3 men and 4 boys will take to finish a work which can be done by 10 men in 8 days is
-
View Hint View Answer Discuss in Forum
According to the question,
1 man ≡ 2 boys
∴ 3 men + 4 boys ≡ (3 + 2) men ≡ 5 men
∴ M1D1 = M2D2
⇒ 5 × D1 = 10 × 8⇒ D1 = 10 × 8 = 16 days 5 Correct Option: B
According to the question,
1 man ≡ 2 boys
∴ 3 men + 4 boys ≡ (3 + 2) men ≡ 5 men
∴ M1D1 = M2D2
⇒ 5 × D1 = 10 × 8⇒ D1 = 10 × 8 = 16 days 5
- A works twice as fast as B. If B can complete a piece of work independently in 12 days, then what will be the number of days taken by A and B together to finish the work?
-
View Hint View Answer Discuss in Forum
A is twice efficient than B.
∴ Time taken by B = 12 days
⇒ Time taken by A = 6 days
∴ (A + B)’s 1 day’s work= 1 + 1 = 2 + 1 = 1 6 12 12 4
∴ Required time = 4 daysCorrect Option: A
A is twice efficient than B.
∴ Time taken by B = 12 days
⇒ Time taken by A = 6 days
∴ (A + B)’s 1 day’s work= 1 + 1 = 2 + 1 = 1 6 12 12 4
∴ Required time = 4 days
