## RD Sharma Solutions for Class 7 Maths Chapter 10 - Unitary Method - Free PDF Download

## FAQs on RD Sharma Class 7 Maths Solutions Chapter 10 - Unitary Method

1. What is Unitary method?

The unitary method is a method in which one finds the unit's value first and then the value of a required number of units. To give an instance, consider a motorcycle that runs 200 km on 20 litres of fuel, so if we have to find out how much it runs on 30 litre fuel.

So, first find number of Km it runs on 1 litre fuel = $\dfrac{200}{20} = 10km$

Now we can find on 30 litres = $10 \times 30 =300 $ km

2. If in a hostel 45 days, food is available for 50 students, find using unitary method for how many days will this food be sufficient for 75 students?

Using Unitary method to solve this we have to find for 1 student then we can go for 75 students

For 50 students, food is sufficient for 45 days

∴ For 1 student, food is sufficient for 45 x 50 days

and for 75 students, food is sufficient for $\dfrac{(45 \times 50)}{75}$ days. i.e., for 30 days.

3. If 12 men or 18 women can do a piece of work in 14 days, then how long will 8 men and 16 women take to finish the work. Find using unitary method?

12 men ≡ 18 women

⇒ 1 man ≡ $\dfrac{18}{12}$ women ≡ $\dfrac{3}{2}$ women

∴ 8 men ≡ $\dfrac{3}{2} \times 8$ = 12 women

∴ 8 men + 16 women = 12 women + 16 women = 28 women

∵ 18 women can do the work in 14 days .

∴ 1 woman can do the same work in (14 $\times$ 18) days.

∴ 28 women will do the same work in $\dfrac{(14 \times 18)}{28}$ days.

∴ Required number of days = $\dfrac{(14 \times 18)}{28}$ = 9 days

4. A contractor undertakes to do a piece of work in 40 days. He engages 100 men at the begining and 100 more after 35 days and completes the work in stipulated time. If he had not engaged the additional men, how many days behind schedule would it be finished?

According to question , we have

[(100 × 35) + (200 × 5)] men can finish the work in 1 day.

4500 men can finish the work in 1 day.

100 men can finish work = $\dfrac{4500}{100}=45$ days

This is 45 - 40 = 5 days behind schedule.

5. How students can score good marks in Mathematics class 7.

Students can score good marks in mathematics class 7 by revising each chapter 2-3 times. They can also solve R.D sharma book for better understanding and revision. Also, they need to solve sample papers to improve their time management and accuracy. Students can solve sample papers on Vedantu site.