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A cooking gas cylinder with gas in it weighs 29.5 kg. The empty cylinder weighs 15.75 kg. What is the weight (in kg) of the gas inside?

Class 7Fractions and DecimalsFractions and Decimals
  • A14.75
  • B14.25
  • C13.75
  • D13.25

Step-by-Step Solution

Pad the first number to 29.50 so the points line up, then 29.50 − 15.75 = 13.75 kg. Skipping the borrow into the whole-number column (29 − 15 = 14) leaves 14.75, which is too big by a whole kilogram.
Answer: C) 13.75

Key idea: Adding and subtracting unlike fractions

Step 1: find the **LCM of the denominators**. Step 2: convert each fraction to an equivalent fraction with that LCM as the new denominator. Step 3: now the fractions are 'like' — add or subtract numerators, keep denominator.

Example: 1/3 + 1/4. LCM of 3 and 4 is 12. Convert: 1/3 = 4/12, 1/4 = 3/12. Add: 4/12 + 3/12 = 7/12.

The whole job is converting once you've picked the right common denominator.

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