Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 1

Question 2.
6 books weigh 1 .260 kg. How many books will weigh 3.150 kg ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 2

Question 3.
8 men complete a work in 6 hours. In how many hours will 12 men complete the same work ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 3

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 4

Question 5.
A typist takes 80 minutes to type 24 pages. How long will he take to type 87 pages ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 5

Question 6.
Rs. 750 support a family for 15 days. For how many days will Rs. 2,500 support the same family ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 6

Question 7.
400 men have provisions for 23 weeks. They are joined by 60 men. How long will the provisions last ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 7

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?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 8

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 9

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 10

Question 11.
If 3 dozen eggs cost Rs. 90, find the cost of 3 scores of eggs. (1 score = 20)
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 11

Question 12.
If the fare for 48 km is Rs. 288, what will be the fare for 36 km ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 12

Question 13.
What will be the cost of 3.20 kg of an item, if 3 kg of it costs Rs. 360 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 13

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 14

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 15

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 16

Question 17.
A man earns ₹5,800 in 10 days. How much will he earn in the month of February of a leap year?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 17

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?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 18

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?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7A 19

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

Question 1.
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B Q1

Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 20

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.
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 21

Question 3.
A wrist watch loses 10 sec in every 8 hours; in how much time will it lose 15 sec. ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 22

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. ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 23

Question 5.
50 men mow 32 hectares of land in 3 days. How many days will 15 men take to mow it?
Answer:

Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 24

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?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 100

Question 7.
If 32 apples weigh 2 kg 800 g. How many apples will there be in a box, containing 35 kg of apples ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 25

Question 8.
A truck uses 20 litres of diesel for 240 km. How many litres will be needed for 1200 km?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 27
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 101

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 28

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7B 29

EXERCISE 7 (C)

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:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 30

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 31

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 32

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 33

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 34

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 ?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 35

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.
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 36

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.
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 37

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:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 38

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?
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 39

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.
Answer:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 7 Unitary Method (Including Time and Work) Ex 7C 40

Selina Concise Mathematics Class 7 ICSE Solutions

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