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## Selina Publishers Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work)

**Selina Publishers Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work)**

### Unitary Method Exercise 7A – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.

Weight of 8 identical articles is 4.8 kg. What is the weight of 11 such articles ?

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Question 2.

6 books weigh 1 .260 kg. How many books will weigh 3.150 kg ?

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Question 3.

8 men complete a work in 6 hours. In how many hours will 12 men complete the same work ?

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Question 4.

If a 25 cm long candle burns for 45 minutes, how long will another candle of the same material and same thickness but 5 cm longer than the previous one, burn ?

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Question 5.

A typist takes 80 minutes to type 24 pages. How long will he take to type 87 pages ?

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Question 6.

Rs. 750 support a family for 15 days. For how many days will Rs. 2,500 support the same family ?

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Question 7.

400 men have provisions for 23 weeks. They are joined by 60 men. How long will the provisions last ?

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Question 8.

200 men have provisions for 30 days. If 50 men left, the same provisions would last for the remaining men, in how many days?

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Question 9.

8 men can finish a certain amount of provisions in 40 days. If 2 more men join with them, find for how many days the same amount of provisions be sufficient ?

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Question 10.

If interest on Rs. 200 be Rs. 25 in a certain time, what will be the interest on Rs 750 for the same time ?

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Question 11.

If 3 dozen eggs cost Rs. 90, find the cost of 3 scores of eggs. (1 score = 20)

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Question 12.

If the fare for 48 km is Rs. 288, what will be the fare for 36 km ?

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Question 13.

What will be the cost of 3.20 kg of an item, if 3 kg of it costs Rs. 360 ?

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Question 14.

If 9 lines of a print, in a column of a book contains 36 words. How many words will a column of 51 lines cqntain ?

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Question 15.

125 pupil have food sufficient for 18 days. If 25 more pupil join them, how long will the food last now ? What assumption have you made to come to your answer ?

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Question 16.

A carpenter prepares a new chair in 3 days, working 8 hours a day. Atleast how many hours per day must he work in order to make the same chair in 4 days ?

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Question 17.

A man earns ₹5,800 in 10 days. How much will he earn in the month of February of a leap year?

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Question 18.

A machine is used for making rubber balls and makes 500 balls in 30 minutes. How many balls will it make in 3\(\frac { 1 }{ 2 }\) hours?

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Question 19.

In a school’s hostel mess, 20 children consume a certain quantity of ration in 6 days. However, 5 children did not return to the hostel after holidays. How long will the same amount of ration last now?

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### Unitary Method Exercise 7B – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.

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Question 2.

3\(\frac { 1 }{ 2 }\)m of cloth costs Rs. 168 ; find the cost of 4\(\frac { 1 }{ 3 }\)m of the same cloth.

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Question 3.

A wrist watch loses 10 sec in every 8 hours; in how much time will it lose 15 sec. ?

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Question 4.

In 2 days and 20 hours, a watch gains 20 sec ; find how much time will the watch take to gain 35 sec. ?

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Question 5.

50 men mow 32 hectares of land in 3 days. How many days will 15 men take to mow it?

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Question 6.

The wages of 10 workers for a six days week are Rs, 1,200. What are the one day wages: (i) of one worker ? (ii) of 4 workers?

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Question 7.

If 32 apples weigh 2 kg 800 g. How many apples will there be in a box, containing 35 kg of apples ?

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Question 8.

A truck uses 20 litres of diesel for 240 km. How many litres will be needed for 1200 km?

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Question 9.

A garrison of 1200 men has provisions for 15 days. How long will the provisions last if the garrison be increased by 600 men ?

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Question 10.

A camp has provisions for 60 pupil for 18 days. In how many days, the same provisions will finish off if the strength of the camp is increased to 72 pupil ?

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### Unitary Method Exercise 7C – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.

A can do a piece of work in 6 days and B can do it in 8 days. How long will they take to complete it together ?

Answer:

Question 2.

A and B working together can do a piece of work in 10 days B alone can do the same work in 15 days. How long will A alone take to do the same work ?

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Question 3.

A can do a piece of work in 4 days and B can do the same work in 5 days. Find, how much work can be done by them working together in : (i) one day (ii) 2 days.

What part of work will be left, after they have worked together for 2 days ?

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Question 4.

A and B take 6 hours and 9 hours respectively to complete a work. A works for 1 hour and then B works for two hours.

(i) How much work is done in these 3 hours ?

(ii) How much work is still left ?

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Question 5.

A, B and C can do a piece of work in 12, 15 and 20 days respectively. How long will they take to do it working together ?

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Question 6.

Two taps can fill a cistern in 10 hours and 8 hours respectively. A third tap can empty it in 15 hours. How long will it take to fill the empty cistern, if all of them are opened together ?

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Question 7.

Mohit can complete a work in 50 days, whereas Anuj can complete the same work in 40 days.

Find:

(i) work done by Mohit in 20 days.

(ii) work left after Mohit has worked on it for 20 days.

(iii) time taken by Anuj to complete the remaining work.

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Question 8.

Joseph and Peter can complete a work in 20 hours and 25 hours respectively.

Find :

(i) work done by both together in 4 hrs.

(ii) work left after both worked together for 4 hrs.

(iii) time taken by Peter to complete the remaining work.

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Question 9.

A is able to complete \(\frac { 1 }{ 3 }\) of a certain work in 10 hrs and B is able to complete\(\frac { 2 }{ 5 }\) of the same work in 12 hrs.

Find:

(i) how much work can A do in 1 hour ?

(ii) how much work can B do in 1 hour ?

(iii) in how much time will the work be completed, if both work together.

Answer:

Question 10.

Shaheed can prepare one wooden chair in 3 days and Shaif can prepare the same chair in 4 days. If they work together, in how many days will they prepare :

(i) one chair ?

(ii)14 chairs of the same kind?

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Question 11.

A, B and C together finish a work in 4 days. If A alone can finish the same work in 8 days and B in 12 days, find how long will C take to finish the work.

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