Worked Example 1
A shopper buys goods costing Rs 245.50, Rs 8.75 and Rs 120.
Write them with the points lined up245.50, 8.75, 120.00 with all three points in one column
Add column by columnRs 374.25
Why the zeros matterWithout them, someone might leave 120 hanging in the wrong columns entirely.
Worked Example 2
A quantity of 0.4 is needed at a rate of 0.3 per unit.
Multiply as if there were no points3 × 4 = 12
Count the digits after the pointsOne plus one is two, so the answer is 0.12
Sense check0.12 passes and 1.2 fails the check.
Where the rule comes from3/10 × 4/10 = 12/100. The counting rule is just a shortcut for that.
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