Exercise 1.5

Exercise 1.5

Miscellaneous practice problems

1. Write the following decimal numbers in the place value table.

(i) 247.36

(ii) 132.105

Answer: 

2. Write each of the following as decimal number.

i) 300 + 5  +  7/10 +   9/100 +    2/1000 = 305792

ii) 1000 + 400 + 30 + 2 +   6/10 + 7/100 = 143267

3. Which is greater?

(i) 0.888 (or) 0.28

The whole number parts of the two decimal numbers are equal.

Comparing the digits of tenth place, 8 > 2

So, 0.888 > 0.28

The greater number is 0.888.

(ii) 23.914 (or) 23.915

The two numbers have same digits upto hundredth place.

But the thousandth place of 5 > 4.

So, 23.915 > 23.914

The greater number is 23.915.

4. In a 25 m swimming competition, the time taken by 5 swimmers A, B, C, D and E are 15.7 seconds, 15.68 seconds, 15.6 seconds, 15.74 seconds and 15.67 seconds respectively. Identify the winner.

The time taken by 5 swimmers A, B, C, D and E are 15.7, 15.68, 15.6, 15.74, 15.67 seconds.

The whole parts of the two decimal numbers are equal.

So, Comparing the tenth place, 6 < 7

The numbers which have 6 in the tenth places are 15.68, 15.6, 15.67.

Comparing the hundred the place,

0 < 7 < 8

So, 15.6 < 15.67 < 15.68

The smaller decimal number is 15.6.

The swimmer who takes less time is the winner.

So, the winner is C (15.6 seconds)

5. Convert the following decimal numbers into fractions.

(i) 23.4

23.4 = 23 + ( 4÷2 / 10÷2 ) = 23 + 2/5

= 23 (2 / 5) = 117 / 5

 (ii) 46.301

46.301 = 46 +   (301 / 1000)

= 46301 / 1000

6. Express the following in kilometres using decimals.

(i) 256 m

 (ii) 4567 m

i) 256 m = 256/1000 km = 0.256 km

ii) 4567 m = 4567/1000 km = 4.567 km

7. There are 26 boys and 24 girls in a class. Express the fractions of boys and girls as decimal numbers.

Number of boys = 26

Number of girls = 24

Total students = 50

Boys = 26×2 / 50×2 = 52 / 100 = 0.52

Girls = 24×2 / 50×2 = 48 / 100 = 0.48

Challenge Problems

8. Write the following amount using decimals.

(i) 809 rupees 99 paise

= 809 +   99/100 = ₹809.99

 (ii) 147 rupees 70 paise

= 147 +   70/100 = ₹ 147.70

9. Express the following in metres using decimals.

(i) 1328 cm

(ii) 419 cm

i) 1328 cm = 1328 / 100 m = 13.28 m

ii) 419 cm = 419 / 100 m = 4.19 m

10. Express the following using decimal notation.

(i) 8 m 30 cm in metres

8 m 30 cm = 8.30 m

(ii) 24 km 200 m in kilometres

24 km 200 m = 24.200 km

11. Write the following fractions as decimal numbers.

(i) 23 / 10000 = 0.0023

(ii) 421 / 100 = 4.21

(iii) 37 / 10 = 3.7

12. Convert the following decimals into fractions and reduce them to the lowest form.

(i) 2.125

(ii) 0.0005

(i) 2.125

= 2 + ( 125÷125 / 1000÷125 ) / 125

= 2 +   1 / 8 = 17 / 8

ii) 0.0005

= 5÷5 / 10000÷5

= 1 / 2000

13. Represent the decimal numbers 0.07 and 0.7 on a number line.

Answer: 

The number line of 0.07 and 0.7.

14. Write the following decimal numbers in words.

(i) 4.9 = Four and nine tenths.

(ii) 220.0 = Two hundred and twenty.

(iii) 0.7 = Seven tenths.

(iv) 86.3 = Eighty six and three tenths.

15. Between which two whole numbers the given numbers lie?

(i) 0.2

0 and 1

(ii) 3.4

3 and 4

(iii) 3.9

3 and 4

(iv) 2.7

2 and 3

(v) 1.7

l and 2

(vi) 1.3

1 and 2

16. By how much is 9 /10 km less than 1 km. Express the same in decimal form.

1 – 9/10 km

10–9  / 10 = 1/10 = 0.1 km

ANSWERS:

Exercise 1.5

1. 

2. (i) 305.792 (ii) 1432.67

3. (i) 0.888 (ii) 23.915

4. C is the winner (15.6 s)

5. (i) 117/5 (ii) 46301/1000

6. (i) 0.256 km (ii) 4.567 km

7. Boys = 0.52; Girls=0.48

Challenge problems

8. (i) ₹809.99 (ii) ₹147.70

9. (i) 13.28 m (ii) 4.19 m

10.(i) 8.30 m (ii) 24.200 km

11. (i) 0.0023 (ii) 4.21 (iii) 3.7

12. (i) 17/8 (ii) 1/2000

13. 

14. (i) four and nine tenths (ii) Two hundred and twenty  (iii) seven tenths (iv) Eighty six and three tenths

15.(i) 0 and 1 (ii) 3 and 4 (iii) 3 and 4 (iv) 2 and 3  (v) 1 and 2 (vi) 1 and 2

16. 0.1 km