Decimal Fractions

decimal fractions

Step by Step solutions of Concise Mathematics ICSE Class-7 Maths chapter 4- Decimal Fractions by Selina is provided.

Table Of Contents
  1. Q1: Convert the following into fractions in their lowest terms:
  2. Q2: Convert into decimal fractions:
  3. Q3: Write the number of decimal places in:
  4. Q4: Write the following decimals as word statements:
  5. Q5: Convert the given fractions into like fractions:
  6. Q1: Add:
  7. Q2: Subtract the first number from the second:
  8. Q3: Simplify:
  9. Q4: Find the difference between 6.85 and 0.685.
  10. Q5: Take out the sum of 19.38 and 56.025 from 200.111.
  11. Q6: Add 13.95 and 1.003, and from the result, subtract the sum of 2.794 and 6.2.
  12. Q7: What should be added to 39.587 to give 80.375?
  13. Q8: What should be subtracted from 100 to give 19.29?
  14. Q9: What is excess of 584.29 over 213.95?
  15. Q10: Evaluate:
  16. Q11: What is the excess of 75 over 48.29?
  17. Q12: If A = 237.98 and B = 83.47. Find:
  18. Q13: The cost of one kg of sugar increases from ₹28.47 to ₹32.65. Find the increase in cost.
  19. Q1: Multiply:
  20. Q2: Multiply each number by 10, 100 and 1000:
  21. Q3: Evaluate:
  22. Q4: Divide:
  23. Q5: Divide each of given numbers by 10, 100, 1000 and 10000:
  24. Q6: Evaluate:
  25. Q7: Evaluate:
  26. Q8: Evaluate:
  27. Q9: Find the cost of 36.75 kg wheat at rate of ₹12.80 per kg.
  28. Q10: The cost of a pen is ₹56.15. Find the cost of 16 such pens.
  29. Q11: Evaluate
  30. Q12: Fifteen identical articles weigh 31.50 kg. Find the weigh of each article.
  31. Q13: The product of two numbers is 211.2. If one of these two numbers is 16.5, find the other number.
  32. Q14: One dozen identical articles cost ₹45.96. Find the cost of each article.
  33. Q15: Find whether the given division forms a terminating or a non-terminating decimal:
  34. Q1: The weight of an object is 306 kg. Find the total weight of 48 similar objects.
  35. Q2: Find the cost of 17.5m cloth at the rate of ₹112.50 per metre.
  36. Q3: One kilogram of oil costs ₹73.40. Find the cost of ₹9.75 kilograms of the oil.
  37. Q4: Total weight of 8 identical objects is 51.2 kg. Find the weight of each object.
  38. Q5: 18.5 m of oil costs ₹ 666. Find the cost of 3.8 m cloth.
  39. Q6: Find the value of:
  40. Q7: Evaluate:
  41. Q1: Which is greater: 5.038 or 5.3?
  42. Q2: Shyama bought 5 kg 300 g apples and 3 kg 250 g mangoes. Saria bought 4 kg 800 g oranges and 4 kg 150 g bananas. Who bought more fruits?
  43. Q3: Two kg of milk contains 0.315 kg of cream. The cream in 20 kg milk is:
  44. Q4: The distance walked by a boy is 86.4 km in 4.8 hours. The distance covered by him in one hour is:
  45. Q5: The number seven and 7 thousandth is:
  46. Q6: (56.56div1.4) is equal to:
  47. Q7: (left(2+frac{1}{2}right)divfrac{3}{5}) is equal to:
  48. Q8: Total cost of two pens at ₹5.30 each and four notebooks at ₹20.50 each is:
  49. Q9: (2.5+3.8div0.02) is equal to:
  50. Q10: By what decimal number should 0.0001 be divided to get 0.01?
  51. Q11: (3frac{1}{5}timesleft(frac{1}{2}+frac{3}{8}right)divfrac{21}{40}) is equal to:
  52. Q12: 5.80, 0.95, 1.87 and 1.92 in descending order are:
  53. Q13: (3-frac{1}{4} of left(15.8-3right)) is equal to:
  54. Q14: Statement 1: (0.05=0.050=0.005=0.00500) Statement 2: Any number of zeros put at the end (i.e. on the right side) of a decimal number does not change its value. Which of the following options is correct?
  55. Q15: Assertion (A): Representation of 6.25 as a vulgar fraction is (6frac{1}{4}). Reason (R): A fraction is said to be a vulgar fraction if the denominator is a whole number but not of the form ({10}^n, nin N).
  56. Q16: Assertion (A): If the product of two decimal numbers is 17.55 and one of them is 6.5, then other one is 2.7. Reason (R): In division of decimal numbers, the dividend is always exactly divisible and no remainder is left after certain steps. Also quotient is always reduced to a terminating decimal.
  57. Q17: Assertion (A): (3.10divleft(0.1times0.1right)=3.1). Reason (R): In division of a decimal number by ({10}^n, nin N), shift the decimal point to the right by as many digits equivalent to n in the power of 10 in the divisor.
  58. Q18: Assertion (A): 9, 9.56, 9.2, 9.005 are all unlike decimals, hence addition operations can't be performed. Reason (R): A whole number can also be expressed as a decimal number by putting a decimal after its unit's digit and after it as many zeroes required to perform addition operations with other like or unlike decimal numbers.

Exercise: 4-A

Q1: Convert the following into fractions in their lowest terms:

i. 3.75

Step 1: Write the decimal as a fraction. \[ 3.75 = \frac{375}{100} \] Step 2: Reduce to lowest terms. \[ \frac{375 \div 25}{100 \div 25} = \frac{15}{4} \] Answer: \(\frac{15}{4}\)

ii. 0.5

Step 1: Write as a fraction. \[ 0.5 = \frac{5}{10} \] Step 2: Reduce to lowest terms. \[ \frac{5 \div 5}{10 \div 5} = \frac{1}{2} \] Answer: \(\frac{1}{2}\)

iii. 2.04

Step 1: Write as a fraction. \[ 2.04 = \frac{204}{100} \] Step 2: Reduce to lowest terms. \[ \frac{204 \div 4}{100 \div 4} = \frac{51}{25} \] Answer: \(\frac{51}{25}\)

iv. 0.65

Step 1: Write as a fraction. \[ 0.65 = \frac{65}{100} \] Step 2: Reduce to lowest terms. \[ \frac{65 \div 5}{100 \div 5} = \frac{13}{20} \] Answer: \(\frac{13}{20}\)

v. 2.405

Step 1: Write as a fraction. \[ 2.405 = \frac{2405}{1000} \] Step 2: Reduce to lowest terms. \[ \frac{2405 \div 5}{1000 \div 5} = \frac{481}{200} \] Answer: \(\frac{481}{200}\)

vi. 0.085

Step 1: Write as a fraction. \[ 0.085 = \frac{85}{1000} \] Step 2: Reduce to lowest terms. \[ \frac{85 \div 5}{1000 \div 5} = \frac{17}{200} \] Answer: \(\frac{17}{200}\)


vii. 8.025

Step 1: Write as a fraction. \[ 8.025 = \frac{8025}{1000} \] Step 2: Reduce to lowest terms. \[ \frac{8025 \div 25}{1000 \div 25} = \frac{321}{40} \] Answer: \(\frac{321}{40}\)


Q2: Convert into decimal fractions:

i. \(2\frac{4}{5}\)

Step 1: Convert to improper fraction: \[ 2\frac{4}{5} = \frac{(2 \times 5) + 4}{5} = \frac{14}{5} \] Step 2: Divide numerator by denominator: \[ \frac{14}{5} = 2.8 \] Answer: 2.8

ii. \(\frac{79}{100}\)

Step 1: Divide numerator by denominator: \[ \frac{79}{100} = 0.79 \] Answer: 0.79

iii. \(\frac{37}{10,000}\)

Step 1: Divide numerator by denominator: \[ \frac{37}{10000} = 0.0037 \] Answer: 0.0037

iv. \(\frac{7543}{{10}^4}\)

Step 1: \({10}^4 = 10000\) \[ \frac{7543}{10000} = 0.7543 \] Answer: 0.7543

v. \(\frac{3}{4}\)

Step 1: Divide numerator by denominator: \[ \frac{3}{4} = 0.75 \] Answer: 0.75

vi. \(9\frac{3}{5}\)

Step 1: Convert to improper fraction: \[ 9\frac{3}{5} = \frac{(9 \times 5) + 3}{5} = \frac{48}{5} \] Step 2: Divide numerator by denominator: \[ \frac{48}{5} = 9.6 \] Answer: 9.6

vii. \(8\frac{5}{8}\)

Step 1: Convert to improper fraction: \[ 8\frac{5}{8} = \frac{(8 \times 8) + 5}{8} = \frac{69}{8} \] Step 2: Divide numerator by denominator: \[ \frac{69}{8} = 8.625 \] Answer: 8.625

viii. \(5\frac{7}{8}\)

Step 1: Convert to improper fraction: \[ 5\frac{7}{8} = \frac{(5 \times 8) + 7}{8} = \frac{47}{8} \] Step 2: Divide numerator by denominator: \[ \frac{47}{8} = 5.875 \] Answer: 5.875


Q3: Write the number of decimal places in:

i. \(0.4762\)

Step 1: Count digits after the decimal point. \[ \text{Digits after decimal in } 0.4762 = 4 \] Answer: 4 decimal places

ii. \(7.00349\)

Step 1: Count digits after the decimal point. \[ \text{Digits after decimal in } 7.00349 = 5 \] Answer: 5 decimal places

iii. \(8235.403\)

Step 1: Count digits after the decimal point. \[ \text{Digits after decimal in } 8235.403 = 3 \] Answer: 3 decimal places

iv. \(35.4\)

Step 1: Count digits after the decimal point. \[ \text{Digits after decimal in } 35.4 = 1 \] Answer: 1 decimal place

v. \(2.608\)

Step 1: Count digits after the decimal point. \[ \text{Digits after decimal in } 2.608 = 3 \] Answer: 3 decimal places

vi. \(0.000879\)

Step 1: Count digits after the decimal point. \[ \text{Digits after decimal in } 0.000879 = 6 \] Answer: 6 decimal places


Q4: Write the following decimals as word statements:

i. \(0.4, 0.9, 0.1\)

Step 1: Express each decimal as “zero-point-” followed by digits read individually.

  • \(0.4\) — zero-point-four
  • \(0.9\) — zero-point-nine
  • \(0.1\) — zero-point-one

Answer: zero-point-four, zero-point-nine, zero-point-one

ii. \(1.9, 4.4, 7.5\)

Step 1: Read the whole number, then say “point” followed by digits individually.

  • \(1.9\) — one-point-nine
  • \(4.4\) — four-point-four
  • \(7.5\) — seven-point-five

Answer: one-point-nine, four-point-four, seven-point-five

iii. \(0.02, 0.56, 13.06\)

Step 1: Read as zero-point- for decimals less than 1 and whole number with point for others.

  • \(0.02\) — zero-point-zero-two
  • \(0.56\) — zero-point-five-six
  • \(13.06\) — thirteen-point-zero-six

Answer: zero-point-zero-two, zero-point-five-six, thirteen-point-zero-six

iv. \(0.005, 0.207, 111.519\)

Step 1: Read digit-by-digit after decimal, starting with zero-point- for decimals less than 1.

  • \(0.005\) — zero-point-zero-zero-five
  • \(0.207\) — zero-point-two-zero-seven
  • \(111.519\) — one hundred eleven-point-five-one-nine

Answer: zero-point-zero-zero-five, zero-point-two-zero-seven, one hundred eleven-point-five-one-nine

v. \(0.8, 0.08, 0.008, 0.0008\)

Step 1: Use zero-point- and read every digit after decimal individually.

  • \(0.8\) — zero-point-eight
  • \(0.08\) — zero-point-zero-eight
  • \(0.008\) — zero-point-zero-zero-eight
  • \(0.0008\) — zero-point-zero-zero-zero-eight

Answer: zero-point-eight, zero-point-zero-eight, zero-point-zero-zero-eight, zero-point-zero-zero-zero-eight

vi. \(256.1, 10.22, 0.634\)

Step 1: Read the whole number, then “point” followed by digits individually.

  • \(256.1\) — two hundred fifty-six-point-one
  • \(10.22\) — ten-point-two-two
  • \(0.634\) — zero-point-six-three-four

Answer: two hundred fifty-six-point-one, ten-point-two-two, zero-point-six-three-four


Q5: Convert the given fractions into like fractions:

i. \(0.5, 3.62, 43.981, \text{ and } 232.0037\)

Step 1: Find the decimal with the greatest number of decimal places. \[ 0.5 = 0.5 \quad (\text{1 decimal place}) \\ 3.62 = 3.62 \quad (\text{2 decimal places}) \\ 43.981 = 43.981 \quad (\text{3 decimal places}) \\ 232.0037 = 232.0037 \quad (\text{4 decimal places}) \]Step 2: Convert all decimals to have the same number of decimal places (4 decimal places, as in 232.0037) by adding zeros. \[ 0.5 = 0.5000 \\ 3.62 = 3.6200 \\ 43.981 = 43.9810 \\ 232.0037 = 232.0037 \]Answer: 0.5000, 3.6200, 43.9810, 232.0037

ii. \(215.78, 33.0006, 530.3, \text{ and } 0.03569\)

Step 1: Find the decimal with the greatest number of decimal places. \[ 215.78 = 215.78 \quad (\text{2 decimal places}) \\ 33.0006 = 33.0006 \quad (\text{4 decimal places}) \\ 530.3 = 530.3 \quad (\text{1 decimal place}) \\ 0.03569 = 0.03569 \quad (\text{5 decimal places}) \]Step 2: Convert all decimals to have the same number of decimal places (5 decimal places, as in 0.03569) by adding zeros. \[ 215.78 = 215.78000 \\ 33.0006 = 33.00060 \\ 530.3 = 530.30000 \\ 0.03569 = 0.03569 \\ \]Answer: 215.78000, 33.00060, 530.30000, 0.03569


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