UPSC Prelims 2020 CSAT Paper II · Q78 of 80 Basic Numeracy easy

If 1 litre of water weighs 1 kg, then how many cubic millimetres of water will weigh 0·1 gm?

  1. (a) 1
  2. (b) 10
  3. (c) 100 ✓ UPSC's answer
  4. (d) 1000

Why the answer is (c)

• 1 litre of water weighs 1 kg, which is equivalent to 1000 grams.

• 1 litre is equal to 1000 cubic centimetres (cm³).

• Therefore, 1000 cm³ of water weighs 1000 grams, meaning 1 cm³ of water weighs 1 gram.

• The question asks for the volume of water that weighs 0.1 grams.

• Since 1 cm³ weighs 1 gram, 0.1 cm³ weighs 0.1 grams.

• Convert 0.1 cm³ to cubic millimetres (mm³): 1 cm³ = 1000 mm³, so 0.1 cm³ = 0.1 × 1000 = 100 mm³.

Why the other options are wrong

(a) 1
1 mm³ of water weighs 0.001 grams, not 0.1 grams.
(b) 10
10 mm³ of water weighs 0.01 grams, not 0.1 grams.
(d) 1000
1000 mm³ of water weighs 1 gram, not 0.1 grams.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

Reading the answer is not the same as getting it right under a clock. Practise this question with UPSC's negative marking, and anything you miss goes into an error notebook until you get it right twice.

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