## RS Aggarwal Class 7 Solutions Chapter 9 Unitary Method Ex 9B

These Solutions are part of RS Aggarwal Solutions Class 7. Here we have given RS Aggarwal Solutions Class 7 Chapter 9 Unitary Method Ex 9B.

**Other Exercises**

- RS Aggarwal Solutions Class 7 Chapter 9 Unitary Method Ex 9A
- RS Aggarwal Solutions Class 7 Chapter 9 Unitary Method Ex 9B
- RS Aggarwal Solutions Class 7 Chapter 9 Unitary Method Ex 9C
- RS Aggarwal Solutions Class 7 Chapter 9 Unitary Method CCE Test Paper

**Question 1.**

**Solution:**

48 men can dig a trench in = 14 days

1 man will dig the trench in = 14 x 48 days (less men more days)

28 men will dig the trench m = \(\frac { 14 x 48 }{ 28 }\) (more men less days)

= 24 days

**Question 2.**

**Solution:**

In 30 days, a field is reaped by = 16 men

In 1 day, it will be reaped by = 16 x 30 (less days, more men)

and in 24 days, it will be reaped by = \(\frac { 16 x 30 }{ 24 }\) men (more days, less men)

= \(\frac { 480 }{ 24 }\)

= 20 men

**Question 3.**

**Solution:**

In 13 days, a field is grazed by = 45 cows.

In 1 day, the field will be grazed by = 45 x 13 cows (less days, more cows)

and in 9 days the field will be grazed by = \(\frac { 45 x 13 }{ 9 }\) cows (more days, less cows)

= 5 x 13 = 65 cows

**Question 4.**

**Solution:**

16 horses can consume corn in = 25 days

1 horse will consume it in = 25 x 16 days (Less horse, more days)

and 40 horses will consume it in = \(\frac { 25 x 16 }{ 40 }\) days (more horses, less days)

= 10 days

**Question 5.**

**Solution:**

By reading 18 pages a day, a book is finished in = 25 days

By reading 1 page a day, it will be finished = 25 x 18 days (Less page, more days)

and by reading 15 pages a day, it will be finished in = \(\frac { 25 x 18 }{ 15 }\) days (more pages, less days)

= 5 x 6 = 30 days

**Question 6.**

**Solution:**

Reeta types a document by typing 40 words a minute in = 24 minutes

She will type it by typing 1 word a minute in = 24 x 40 minutes (Less speed, more time)

Her friend will type it by typing 48 words 24 x 40 a minute in = \(\frac { 24 x 40 }{ 48 }\) minutes

(more speed, less time)

= 20 minutes

**Question 7.**

**Solution:**

With a speed of 45 km/h, a bus covers a distance in = 3 hours 20 minutes

= 3\(\frac { 1 }{ 3 }\) = \(\frac { 10 }{ 3 }\) hours

With a speed of 1 km/h it will cover the distance m = \(\frac { 10 x 45 }{ 3 }\) h

(Less speed, more time)

and with a speed of 36 km/h, it will cover the distance in

= \(\frac { 10 x 45 }{ 3 x 36 }\) hr (more speed, less time)

= \(\frac { 25 }{ 6 }\) h

= 4\(\frac { 1 }{ 6 }\) h

= 4 hr 10 minutes

**Question 8.**

**Solution:**

To make 240 tonnes of steel, material is sufficient in = 1 month or 30 days

To make 1 tonne of steel, it will be sufficient in = 30 x 240 days (Less steel, more days)

To make 240 + 60 = 300 tonnes of steel it will be sufficient in = \(\frac { 30 x 240 }{ 300 }\) days

= 24 days (more steel, less days)

**Question 9.**

**Solution:**

In the beginning, number of men = 210

After 12 days, more men employed = 70

Total men = 210 + 70 = 280

Total period = 60 days.

After 12 days, remaining period = 60 – 12 = 48 days

Now 210 men can build the house in = 48 days

and 1 man can build the house in = 48 x 210 days (less men, more days) .

280 men can build the house in = \(\frac { 48 x 210 }{ 280 }\) days

(more men, less days)

= 36 days

**Question 10.**

**Solution:**

In 25 days, the food is sufficient for = 630 men

In 1 day, the food will be sufficient for = 630 x 25 men (less days, more men)

and in 30 days, the food will be sufficient for = \(\frac { 630 x 25 }{ 30 }\) hr

(more days less men)

= 525 men

Number of men to be transfered = 630 – 525 = 105 men

**Question 11.**

**Solution:**

Number of men in the beginning = 120

Number of men died = 30

Remaining = 120 – 30 = 90 men

Total period = 200 days

No. of days passed = 5

Remaining period = 200 – 5 = 195

Now, The food lasts for 120 men for = 195 days

The food will last for 1 man for = 195 x 120 days (Less men, more days)

The food will last for 90 men for = \(\frac { 195 x 120 }{ 90 }\)

(more men less days)

= 65 x 4 = 260 days

**Question 12.**

**Solution:**

Period in the beginning = 28 days

No. of days passed = 4 days.

Remaining period = 28 – 4 = 24 days

The food is sufficient for 24 days for = 1200 soldiers

The food will be sufficient for 1 day for = 1200 x 24 soldiers (Less days, more men)

and the food will be sufficient for 32 days = \(\frac { 1200 x 24 }{ 32 }\)

= 900 soldiers (more days, less men)

No. of soldiers who left the fort = 1200 – 900 = 300 soldiers

Hope given RS Aggarwal Solutions Class 7 Chapter 9 Unitary Method Ex 9B are helpful to complete your math homework.

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