untitled

Solution : Let, Rafiq and Shafiq together can finish the wok in d days.
Let us make the following table :

Name Number of days

for doing the work

Part of the work

done in 1 day

Work done

ind days

Rafiq 10

10

1

10

d

Shafiq 15

15

1

15

d

By the questions, 1
10 15



d d

or, 1
15

1

10

1

̧

¹

̈ ·

©

d§ 

or, 1
30

3 2

̧

¹

·

̈

©

§ 

d

or, 1
30

5

d

or, 6
5
d 30

? They together can finish the work in 6 days.
Example 3. A boatman can go x km in time t 1 hour against the current. To cover

that distance along the current he takes t 2 hour. How much is the speed of the boat
and the current.
Solution : Let the speed of the boat in still water be u km per hour and that of the
current be v km per hour.
Then, along the current, the effective speed of boat is (uv) km per hour and
against the current, the effective speed of boat is (uv) km per hour.

According to the question,

.......()

2

i

t

x

uv [

time

distance traversed

speed ]

and .......()
1

ii

t

x

uv

Adding equations (i) and (ii) we get,

̧ ̧

¹

·

̈ ̈

©

§

 

1 2 1 2

1 1

2

t t

x

t

x

t

x

u