NCERT Solutions for Class 4 Mathematics Unit-6 The Junk Seller

NCERT Textbook Page 60
1. What about you? Do you also find Maths difficult?
Ans. No. I do not find Maths difficult. It becomes easy if it is practised well regularly.

2. What is the most difficult thing in your Maths book?
Ans. Nothing, all topics look easy to me.

3. What do you think is the easiest lesson?
Ans. All lessons are of equal level. This depends upon a lot of practice of maths.

NCERT Textbook Page 61
Find out: How much for a cup of tea?
1. Ask people and find out the cost of a cup of tea –
• At a tea stall
Ans. At a tea stall a cup of tea costs Rs 3.
• At a hotel
Ans. At a hotel a cup of tea costs Rs 5.

2. If a person who runs a tea stall earns ? 30 a $ay, how much will he earn in 10 days?
Ans.
Earning in 1 day = Rs 30 x 1
Therefore, earning in 2 days = Rs 30 x 2
Earning in 3 days = Rs 30 x 3
And so on_______
Earning in 10 days = Rs 30 x 10 = 300
•And in a month?
Ans.
A month has 30 days
If earning in 1 day = Rs 30
Therefore, earning in 30 days = Rs 30 X 30 = Rs 900.

FindOut: What is a Loan?
1. Have you ever heard of someone taking a loan? For what?
Ans.I heard a person took loan. He took loan to start his shop.

2. How much loan was taken?
Ans. He took Rs 10,000.

3. How much money was paid back?
Ans.He paid back Rs 11,000 after one year.

4. Who has to pay back more-Hariya or Babu?
Ans.Hariya has to pay Rs 51 every month for six months.
Total money he has to pay = 51 x 6 = Rs 306 Babu has to pay Rs 360
Hence, Babu will have to pay back more money.

NCERT Textbook Page 62
1. How much does Kiran earn from 9 rickshaws in a day?
Ans. From one rickshaw she earns = Rs 20
From 2 rickshaws she will earn = Rs 20 x 2
From 3 rickshaws she will earn = Rs 20 x 3
Similarly from 9 rickshaws she will earn = Rs 20 x 9 = Rs 180
That is 9 times 20.

2. For 10 rickshaws she will get Rs 20 x 10 = Rs 200.
So, for 9 rickshaws, she will get Rs 200 – _____ = ______
Ans. For 9 rickshaws she will get Rs 200 – 20 = Rs 180.

NCERT Textbook Page 63
1. Ina week how much does Kiran earn from one rickshaw?
Ans. There are 7 days in a week.
In 1 day Kiran earns from one rickshaw = Rs 20
So, in 7 days Kiran will earn from one rickshaw = Rs 20 x 7 = Rs 140.

2. Do it mentally and write the answers
2 x 6 = ________ 4 x 80 = ________
20 x 6 = ________ 4 x 81 = ________
2 x 60 = ________ 9 x 25 = ________
3 x 42 = ________ 31 x 9 = ________
Ans.
2 x 6 = 12 4 x 80 = 320
20 x 6 = 120 4 x 81 = 324
2 x 60 = 120 9 x 25 = 225
3 x 42 = 126 31 x 9 = 279

How Much to Pay for this Junk?
3. How much will Kiran pay for 31 kg newspaper?
Ans. The cost of 1 kg of newspaper = Rs 5
So, the cost of 31 kg of newspaper = Rs 5 x 31
= Rs 155.

NCERT Textbook Page 64

1. How much will Kiran pay for 42 kg newspaper?
Ans. Kiran pays for 1 kg of newspaper = Rs 5
So, she will pay for 42 kg of newspaper = Rs 15 x 42
= Rs 210.

2. Also find the cost of • 22 kg of plastic
Ans. Rate of 1 kg of plastic = Rs 10
Therefore, cost of 22 kg of plastic = Rs 10 x 22
= Rs 220.
• 23 kg of waste paper
Ans. The cost of 1 kg of waste paper = Rs 4
Therefore, the cost of 23 kg of waste paper = Rs 4 x 23
= Rs 92.
• 12 kg of iron
Ans. The cost of 1 kg of iron = Rs 12
Therefore, the cost of 12 kg of iron = Rs 12 x 12
= Rs 144.

3. Guess the total money Kiran will pay to the junk collectors. Will it be: — More than 600?
— Less than 600?
Ans. The total money Kiran will pay to the junk collectors
The cost of 42 kg of newspaper = Rs 210
The cost of 22 kg of plastic = Rs 220
The cost of 23 kg of waste paper = Rs 92
The cost of 12 kg of iron = Rs 144
Total cost of all junks = Rs 666
Hence Kiran will pay more than Rs 600.

NCERT Textbook Pages 64-66
Smart Kiran Sells the Junk

1. Kiran bought 1 kg plastic for Rs 10, but sold 1 kg plastic for Rs 12. How much
money does she earn on selling 1 kg plastic? Rs _______
Ans. Kiran bought 1 kg plastic for Rs 10 and sold 1 kg plastic for Rs 12 So, she earn Rs 12 – Rs 10 = Rs 2.
• So, how much money does she earn for 63 kg? Rs _______
Ans. For 1 kg plastic she earns Rs 2.
Therefore, for 63 kg plastic she earns = Rs 2 x 63
= Rs 126
It can be calculated as follows:

You will get 126 by adding the digits in last row.
B. Kiran sells 32 kg iron.

2. How much money will Dinu pay for 32 kg iron?
Ans. 1 kg of plastic is sold in Rs 14
Therefore, 32 kg of plastic = Rs 14 x 32 = Rs 448 This can be calculated in similar manner

You can get the desired numbers by adding the numbers in bold
300 + 20 + 120 + 8 = 448
So, Dinu will pay Rs 448 for 32 kg of plastic.

3. Kiran buys 1 kg iron for Rs 12, but sells it for Rs 14. How much does she earn when she sells 32 kg iron?
Ans. Kiran earns by selling 1 kg of iron = Rs 14 – Rs 12
= Rs 2
So, she will earn by selling 32 kg of iron = Rs 2 x 32
= Rs 64
This can be calculated as follows also.

You will get the desired result by adding the numbers in last row
Which will be equal to 60 + 4 = 64
Hence, Kiran earns Rs 64 by selling 32 kg of iron.
C. What will Dinu pay for 152 kg newspaper?

4. I bought 1 kg newspaper for Rs 5, but sold it for Rs 6. How much money did I earn by selling 152 kg of newspaper?
Ans. She earn by selling 1 kg of newspaper
= Selling price of newspaper – Purchasing price of newspaper
=Rs 6-Rs 5 = Rs 1
Hence, she earned by selling 152 kg newspaper
= Rs 1 x 152 = Rs 152.
D. What does Dinu pay for brass?

5. How much money will Dinu pay for 4 kg brass?
Ans. The rate of 1 kg of brass according to Dinu’s price list = Rs 180
So, Dinu will pay for 4 kg of brass = Rs 180 x 4
= Rs 720
This can be calculated as follows:

By adding the digits in last row you will get 400 + 320 = 720 Hence, Dinu will pay Rs 720 for 4 kg of brass.

NCERT Textbook Page 67
1. First, guess the answer and then calculate
(a) 37 x 18 = (b) 45 x 24 = (c) 69 x 52 =
(e) 142 x 5 = (f) 382 x 3 = (g) 2 x 175 =
(d) 77 x 55 = (ft)4 x 206 =
Ans.
(a) Guess = 37 x 18 means 40 x 20 = about 800
Calculation

By adding the digits in third and fifth rows you will get
300 + 70 + 240 + 56 = 666
Hence, 37 x 18 = 666.
(b) Guess 45 x 24
Then will be near to 40 x 25 = 1000
By Calculation

By adding the numbers in third and fifth rows you will get
800 + 100 + 160 + 20 = 1080
So, 45 x 24 = 1080.
(c) On guessing 69 x 52, the numbers will be near to 70 x 50 = 3500
Calculation

By adding the numbers in third and fifth rows you will get
3000 + 450 + 120 + 18 = 3588
So, 69 x 52 = 3588.
(d) On guessing 77 x 55
The numbers will be near to 80 x 50 = 4000
Calculation:

By adding the numbers in third and fifth rows you will get
3500 + 350 + 350 + 35 = 4235
Hence, 77 x 55 = 4235.
(e) On guessing 142 x 5
The number will be near to 140 x 5 = 700
On calculation

By adding the numbers in last row you will get
500 + 200 + 10 = 710 .
Hence, 142 x 5 = 710.
(f) 382 x 3
On guessing this number will be near to 380 x 3 = 1140
On calculation:

By adding the numbers in last row you will get
900 + 240 + 6 = 1146
So,-382 x 3 = 1146.
(g) 2 x 175
This number will be near to 2 x 175 = 350
On calculation:

By adding numbers in last row you will get
200 + 140 + 10 = 350.
(h) 4 x 206
This number will be near to 5 x 200 = 1000
On calculation:

By adding the numbers in last row you will get
800 + 24 = 824
So, 4 x 206 = 824.