NCERT Answers for Class 7 Maths
Chapter 2 Fractions and Decimals Exercise 2.5
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Chapter 2 Exercise 2.1 |
Page 47-48
Ex 2.5 Class 7 Maths Question 1. Which is greater?
(i) 0.5 or 0.05 (ii) 0.7 or 0.5 (iii) 7 or 0.7
(iv) 1.37 or 1.49 (v) 2.03 or 2.30 (vi) 0.8 or 0.88.
1. Which is grater?
(i) 0.5 or 0.05
Answer
By comparing whole number, 0 = 0
By comparing the tenths place digit, 5 > 0
∴ 0.5 > 0.05
(ii) 0.7 or 0.5
Answer
By comparing whole number, 0 = 0
By comparing the tenths place digit, 7 > 5
∴ 0.7 > 0.5
(iii) 7 or 0.7
Answer
By comparing whole number, 7 > 0
∴ 7 > 0.7
(iv) 1.37 or 1.49
Answer
By comparing whole number, 1 = 1
By comparing the tenths place digit, 3 < 4
∴ 1.37 < 1.49
(v) 2.03 or 2.30
Answer
By comparing whole number, 2 = 2
By comparing the tenths place digit, 0 < 3
∴ 2.03 < 2.30
(vi) 0.8 or 0.88
Answer
By comparing whole number, 0 = 0
By comparing the tenths place digit, 8 = 8
By comparing the hundredths place digit, 0 < 8
∴ 0.8 < 0.88
Ex 2.5 Class 7 Maths Question 2. Express as rupees using decimals :
(i) 7 paise (ii) 7 rupees 7 paise (iii) 77 rupees 77 paise
(iv) 50 paise (v) 235 paise.
2. Express as rupees as decimals:
(i) 7 paise
Answer
We know that,
= ₹ 1 = 100 paise
= 1 paise = ₹ (1/100)
∴ 7 paise = ₹ (7/100)
= ₹ 0.07
(ii) 7 rupees 7 paise
Answer
We know that,
= ₹ 1 = 100 paise
= 1 paise = ₹ (1/100)
∴ 7 rupees 7 paise = ₹ 7 + ₹ (7/100)
= ₹ 7 + ₹ 0.07
= ₹ 7.07
(iii) 77 rupees 77 paise
Answer
We know that,
= ₹ 1 = 100 paise
= 1 paise = ₹ (1/100)
∴ 77 rupees 77 paise = ₹ 77 + ₹ (77/100)
= ₹ 77 + ₹ 0.77
= ₹ 77.77
(iv) 50 paise
Answer
We know that,
= ₹ 1 = 100 paise
= 1 paise = ₹ (1/100)
∴ 50 paise = ₹ (50/100)
= ₹ 0.50
(v) 235 paise
Answer
We know that,
= ₹ 1 = 100 paise
= 1 paise = ₹ (1/100)
∴ 235 paise = ₹ (235/100)
= ₹ 2.35
Ex 2.5 Class 7 Maths Question 3. (i) Express 5 cm in metre and kilometre (ii) Express 35 mm in cm, m and km
Answer
We know that,
= 1 meter = 100 cm
Then,
= 1 cm = (1/100) m
= 5 cm = (5/100)
= 0.05 m
Now,
= 1 km = 1000 m
Then,
= 1 m = (1/1000) km
= 0.05 m = (0.05/1000)
= 0. 00005 km
(i) Express 35 mm in cm, m and km
Answer
We know that,
= 1 cm = 10 mm
Then,
= 1 mm = (1/10) cm
= 35 mm = (35/10) cm
= 3.5 cm
And,
= 1 meter = 100 cm
Then,
= 1 cm = (1/100) m
= 3.5 cm = (3.5/100) m
= (35/1000) m
= 0.035 m
Now,
= 1 km = 1000 m
Then,
= 1 m = (1/1000) km
= 0.035 m = (0.035/1000)
= 0. 000035 km
Ex 2.5 Class 7 Maths Question 4. Express in kg:
(i) 200 g (ii) 3470 g (iii) 4 kg 8 g
(i) 200 g
Answer
We know that,
= 1 kg = 1000 g
Then,
= 1 g = (1/1000) kg
= 200 g = (200/1000) kg
= (2/10)
= 0.2 kg
(ii) 3470 g
Answer
We know that,
= 1 kg = 1000 g
Then,
= 1 g = (1/1000) kg
= 3470 g = (3470/1000) kg
= (3470/100)
= 3.470 kg
(ii) 4 kg 8 g
Answer
We know that,
= 1 kg = 1000 g
Then,
= 1 g = (1/1000) kg
= 4 kg 8 g = 4 kg + (8/1000) kg
= 4 kg + 0.008
= 4.008 kg
Ex 2.5 Class 7 Maths Question 5. Write the following decimal numbers in the expanded form:
(i) 20.03 (ii) 2.03 (iii) 200.03 (iv) 2.034
(i) 20.03
Answer
20.03 = (2 × 10) + (0 × 1) + (0 × (1/10)) + (3 × (1/100))
(ii) 2.03
Answer
2.03 = (2 × 1) + (0 × (1/10)) + (3 × (1/100))
(iii) 200.03
Answer
200.03 = (2 × 100) + (0 × 10) + (0 × 1) + (0 × (1/10)) + (3 × (1/100))
(iv) 2.034
Answer
2.034 = (2 × 1) + (0 × (1/10)) + (3 × (1/100)) + (4 × (1/1000))
Ex 2.5 Class 7 Maths Question 6. Write the place value of 2 in the following decimal numbers:
(i) 2.56 (ii) 21.37 (iii) 10.25 (iv) 9.42 (v) 63.352
(i) 2.56
Answer
From the question, we observe that,
The place value of 2 in 2.56 is ones
(ii) 21.37
Answer
From the question, we observe that,
The place value of 2 in 21.37 is tens
(iii) 10.25
Answer
From the question, we observe that,
The place value of 2 in 10.25 is tenths.
(iv) 9.42
Answer
From the question, we observe that,
The place value of 2 in 9.42 is hundredth.
(v) 63.352
Answer
From the question, we observe that,
The place value of 2 in 63.352 is thousandth.
Ex 2.5 Class 7 Maths Question 7. Dinesh went from place A to place B and from
there to place C. A is 7.5 km from B and B is 12.7 km from C. Ayub went from place A to place D and from there to place C. D is 9.3 km from A and C is 11.8 km from D. Who travelled more and by how much?
Answer
From the question, it is given that,
Distance travelled by Dinesh = AB + BC
= 7.5 + 12.7
= 20.2 km
∴ Dinesh travelled 20.2 km
Distance travelled by Ayub = AD + DC
= 9.3 + 11.8
= 21.1 km
∴ Ayub travelled 21.1km
Clearly, Ayub travelled more distance by = (21.1 – 20.2)
= 0.9 km
∴ Ayub travelled 0.9 km more than Dinesh.
Ex 2.5 Class 7 Maths Question 8. Shyama bought 5 kg 300 g apples and 3 kg 250 g mangoes. Sarala bought 4 kg 800 g oranges and 4 kg 150 g bananas. Who bought more fruits?
Answer
From the question, it is given that,
Fruits bought by Shyama = 5 kg 300 g
= 5 kg + (300/1000) kg
= 5 kg + 0.3 kg
= 5.3 kg
Fruits bought by Sarala = 4 kg 800 g + 4 kg 150 g
= (4 + (800/1000)) + (4 + (150/1000))
= (4 + 0.8) kg + (4 + .150) kg
= 4.8 kg + 4.150kg
= 8.950 kg
So, Sarala bought more fruits.
Ex 2.5 Class 7 Maths Question 9. How much less is 28 km than 42.6 km?
Answer
Now, we have to find the difference of 42.6 km and 28 km
42.6 -28.0 = 14.6
∴ 14.6 km less is 28 km than 42.6 km.