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Hardness of water is due to calcium and magnesium ions. Sodium salts dissolve in water and hence lather is formed. When soap is added to hard water, calcium and magnesium ions replaces sodium (or potassium) ions in the soap and gets precipitated hence lather formation is hindered. Thus, this method can be employed to test the hardness of water.
Find the unknown value of' x' in the proportion $$(5x + 1) : 3 = (x + 3) : 7
? % of 1200 = 20% of 30% of 3600
Find the value of ‘y’ if (2/7) × y = 0.79 – 1.77 ÷ 3.
(6.013 – 20.04) = ? + 9.98% of 5399.98
15.50% of 6240 – 426.31 = ?
Evaluate: (768÷16)×(125÷25)−(81÷9)×12
44.99% of 499.98 × (3.30/7.40)% of 1399.97 + 10.02 = ?
690 ÷ (75% of 460) = ? ÷ (50% of 160)
((1024)n/5 × (42n+1 ))/(16n × 4n-1 ) = ?
