Question

212. Dorji takes double the time than Dawa to dig a garden. If Dawa takes 2 hours 30 mins to dig the garden alone,how long will it takes to dig the garden together? (2017PE)
A. 1 hour and 40 mins
B.1 houd and 30 mins
C.1 hour and 20 mins
D. 1 hour and 10 mins

Answer 1

Answer:

We are given that Dorji takes twice the time than Dawa to dig a garden and we have

Dawa can dig a garden in = 2 hrs 30 min = 2\frac{30}{60} = 2\frac{1}{2} = \frac{5}{2}\:hrs2

60

30

=2

2

1

=

2

5

hrs

∴ To dig the same garden, Dorji will take = 2\times \frac{5}{2} = 5\:hrs2×

2

5

=5hrs

So, we can say that

In 1 hr, Dawa will dig = \frac{1}{\frac{5}{2} } = \frac{2}{5} \:of \:the\:garden

2

5

1

=

5

2

ofthegarden

and

In 1 hr, Dorji will dig = \frac{1}{5} \:of \:the\:garden

5

1

ofthegarden

Now,

In 1 hr, both Dawa and Dorji together will dig,

= \frac{2}{5} + \frac{1}{5}

5

2

+

5

1

= \bold{\frac{3}{5} }

5

3

∴ Both Dawa & Dorji will take = \frac{5}{3} \:hrs = 1 \frac{2}{3} \:hrs = 1\: hr\: 40\: mins

3

5

hrs=1

3

2

hrs=1hr40mins to dig a garden.

Thus, it will take 1 hr 40 minutes to dig the garden together.