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PrintSouth African Mathematics Olympiad First Round
South Africa algebra
Problem
Water pours into a tank at a constant rate. After 2 hours the tank was 36% full and after 10 hours it is 100% full. How full was the tank to begin with? (A) 10% (B) 12% (C) 15% (D) 18% (E) 20%
Solution
In 8 hours (from 2 hours to 10 hours), the tank filled up a further (from to ). That is per hour.
So in the first two hours it filled up , meaning it started with .
So in the first two hours it filled up , meaning it started with .
Final answer
E
Techniques
Simple Equations