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Suppose 2 kg of sugar contains 9 × 106 crystals. How many sugar crystals are there in i. 5 kg of sugar? ii. 1.2 kg of sugar?

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Question

Suppose 2 kg of sugar contains 9 × 106 crystals.

How many sugar crystals are there in

  1. 5 kg of sugar?
  2. 1.2 kg of sugar?
Sum
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Solution

i. Let the number of sugar crystals in 5 kg of sugar be x.

The given information, in the form of a table, is as follows:

Amount of sugar (in kg) 2 5
Number of crystals 9 × 106  x

The amount of sugar and the number of crystals it contains are directly proportional to each other. Therefore, we obtain

⇒ `2/(9xx10^6) = 5/x`

⇒ x = `(5xx9xx10^6)/2`

⇒ x = `(5xx9xx100000)/2`

⇒ x = 2.25 × 107

Hence, the number of sugar crystals is 2.25 × 107

ii. Let the number of sugar crystals in 1.2 kg of sugar be y. The given information, in the form of a table, is as follows:

Amount of sugar (in kg) 2 1.2
Number of crystals 9 × 106  y

⇒ `2/1.2 = (9xx10^6)/y`

⇒ `y = (1.2xx9xx10^6)/2`

⇒ y = 5.4 × 106

Hence, the number of sugar crystals is 5.4 x 106

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Chapter 11: Direct and Inverse Proportions - EXERCISE 11.1 [Page 136]

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NCERT Mathematics [English] Class 8
Chapter 11 Direct and Inverse Proportions
EXERCISE 11.1 | Q 7. | Page 136

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