CRE 2 - Working in Shifts | Time & Work

1. CRE 2 - Working in Shifts | Time & Work

A alone can do a piece of work in 15 days and B alone can do it in 20 days. Both A and B worked together for 4 days and then A left. In how many more days will B finish the remaining work?

(a)
$9 \frac{4}{11}$
(b)
$10 \frac{5}{8}$
(c)
$10 \frac{2}{3}$
(d)
$9 \frac{1}{8}$

Answer: Option C

Explanation :

Method 1:
(A + B)’s 4 days work = $4 (\frac{1}{15} + \frac{1}{20})$ = $\frac{7}{15}$

Remaining work = (1 - 7/15) = 8/15;

Now, $\frac{1}{20}$ th work is finished by B in 1 day.

∴ $\frac{8}{15}$ th work will be finished by B in $\frac{8 / 15}{1 / 20}$ = $\frac{8 \times 20}{15}$ = $\frac{32}{3}$ = $10 \frac{2}{3}$

Method 2:
Let the total work to be done = LCM(15, 20) = 60 units.
Efficiency of A = 60/15 = 4 units/day
Efficiency of B = 60/20 = 3 units/day

A and B work for 4 days and then let B finish the remaining work in x days.

∴ Total work done = Work done by A and B in 4 days + Work done by B in x days

⇒ 60 = (4 + 3) × 4 + 3 × x
⇒ 60 = 28 + 3x
⇒ 3x = 32
⇒ x = $\frac{32}{3}$ = $10 \frac{2}{3}$

Method 3:
Let the total work to be done = LCM(15, 20) = 60 units.
Efficiency of A = 60/15 = 4 units/day
Efficiency of B = 60/20 = 3 units/day

A works for 4 days and B work for 4 + x days

∴ Total work done = Work done by A in 4 days + Work done by B in 4 + x days

⇒ 60 = 4 × 4 + (4 + x) × 3
⇒ 60 = 28 + 3x
⇒ 3x = 32
⇒ x = $\frac{32}{3}$ = $10 \frac{2}{3}$

Hence, option (c).

2. CRE 2 - Working in Shifts | Time & Work

A alone can do a certain job in 25 days while B alone can do the same in 20 days. A started the work and was joined by B after 5 days. The number of days taken to complete the entire work will be:

(a)
50/9
(b)
140/9
(c)
125/9
(d)
130/9

3. CRE 2 - Working in Shifts | Time & Work

It takes Mr. Aakash ‘a’ hours to complete typing a manuscript. After 3 hours, he was called away. What fractional part of the assignment was left incomplete?

(a)
1/a
(b)
(a - 2)/a
(c)
a/2
(d)
a - 2
(e)
(a - 3)/a

4. CRE 2 - Working in Shifts | Time & Work

A and B can do a piece of work in 21 and 24 days respectively. They start the work together and after some days A leaves the work and B completes the remaining work in 9 days. After how many days did A leave?

(a)
5
(b)
7
(c)
8
(d)
6

5. CRE 2 - Working in Shifts | Time & Work

How many more days are required to complete the work?

(a)
8 days
(b)
10 days
(c)
12 days
(d)
15 days
(e)
16 days

6. CRE 2 - Working in Shifts | Time & Work

A can build a wall in 24 days, B can do the same in 32 days and C can do in 48 days. Totally 12 walls are to be built. 'A' does the work for first 64 days and 'B' continues the work for the next 24 days. How many days should C work?

(a)
412
(b)
332
(c)
50
(d)
64
(e)
None of these

7. CRE 2 - Working in Shifts | Time & Work

If 1/8^th out of x members are absent, then work increased for each person is:

(a)
x/7
(b)
1/7x
(c)
7/x
(d)
2x/7
(e)
2/7x

Answer: Option B

Explanation :

Let the total work to be done = 1 unit

Number of persons originally scheduled to work = x

Work done by each person (w) = $\frac{1}{x}$

Given 1/8 members are absent, so number of persons present = x – $\frac{x}{8}$ = x $(1 - \frac{1}{8})$ = $\frac{7 x}{8}$

∴ Work done by each person in second case (w’) = $\frac{1}{7 x / 8}$ = $\frac{8}{7 x}$

Extra work by each person in second case = w’ – w = $\frac{8}{7 x}$ – $\frac{1}{x}$ = $\frac{1}{7 x}$

Hence, option (b).

8. CRE 2 - Working in Shifts | Time & Work

A alone can complete a task in 27 days while B alone can complete the same task in 45 days. Both of them started the work together, but A left 5 days before actual completion of work. Find how many days did a work?

(a)
20 days
(b)
15 days
(c)
25 days
(d)
5 days
(e)
10 days

9. CRE 2 - Working in Shifts | Time & Work

A alone can complete a task in 56 days while B alone can complete the same task in 42 days. A and B. A and B took upon the work to complete it together. However, A left 12 days before the scheduled completion of work. Find how many days did B work alone?

(a)
12
(b)
9
(c)
21
(d)
Cannot be determined
(e)
None of these

Answer the next 2 questions based on the information given below.

A is twice as efficient as B and B is twice as efficient as C. If A, B and C work together, a piece of work will be completed in 12 days. A and B start it together and continue for 8 days. After that, A is replaced by C. For his work, A gets paid Rs. 2000.

10. CRE 2 - Working in Shifts | Time & Work

What amount will B get paid?

(a)
Rs. 2000
(b)
Rs. 2500
(c)
Rs. 2650
(d)
Rs. 2733.33
(e)
Rs. 2800

CRE 2 - Working in Shifts | Time & Work

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