Model 3 Man leaves & joins Practice Questions Answers Test with Solutions & More Shortcuts

Answer: (b)

Part of the work done by A and B in 4 days

= $4(1/12 + 1/15) = 4({5 + 4}/60)$

= $4 × 9/60 = 3/5$

Remaining work = $1 - 3/5 = 2/5$

Time taken by B to complete the remaining work

= $2/5 × 15$ = 6 days

Using Rule 20,

Here, m = 12, n = 15, p = 4

B alone do the works in= ${mn - p(m + n)}/m$

= ${12 × 15 - 4(12 + 15)}/12$

= ${180 - 108}/12 = 72/12$ = 6 days

Answer: (c)

B’s 1 day's work

= $1/12 - 1/20 = {5 - 3}/60 = 1/30$

B's $1/2$ day’s work = $1/60$

(A + B)'s 1 day's work

= $1/20 + 1/60 = {3 + 1}/60 = 1/15$

[Since, B works for half day daily]

Hence, the work will be completed in 15 days.

Answer: (d)

Let A and B worked together for x days

According to the question,

Part of work done by A for (x + 10) days

+ part of work done by B for x days = 1

${x + 10}/20 + x/30$ = 1

${3x + 30 + 2x}/60 = 1$

5x + 30 = 60

5x = 30 ⇒ x = $30/5$ = 6 days

Here, m =20, n= 30, p = x and time taken by A alone = 10

10 = ${mn - p(m + n)}/n$

10 = ${30 × 20 - x(30 + 20)}/30$

300 = 600 - x 50

50x = 300 x = 6

B worked for 6 days

Answer: (d)

Work done in first two days

= ${2/30 + 1/20 + 1/10 = 1/15 + 1/20 + 1/10$

= ${4 + 3 + 6}/60 = 13/60$

Work done in first 8 days = $52/60$

Remaining work

= $1 - 52/60 = 8/60 = 2/15$

(A + B)’s 1 day’s work

= $1/30 + 1/20 = {2 + 3}/60 = 1/12$

Remaining work = $2/15 - 1/12$

= ${8 - 5}/60 = 3/60 = 1/20$

(A + C)’s 1 day’s work

= $1/30 + 1/10 = {1 + 3}/30 = 2/15$

Time taken = $1/20 × 15/2 = 3/8$ day

Total time = $9 + 3/8 = 9{3}/8$ days

Answer: (b)

Part of work done by B in 10 days

= 10 × $1/15 = 2/3$

Remaining work = $1 - 2/3 = 1/3$

Time taken by A = $1/3 × 18$ = 6 days