Age Model Question

by Anonymous
(Country Unknown)

A is 40% of his brother's age. In 21 years time, A is 75% of his brother's age. What is A's age now?

Here's My Answer
by Zach
(Singapore)

Step 1: This question involves the Constant Difference Concept. For Percentage questions, more often than not, it is easier to convert the percentages to fractions to facilitate drawing of models. Since A is 40% of his brother's age, we draw 2 boxes to represent A's 40% and 5 boxes to represent his brother's 100%.

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