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MUST-KNOW PSLE MATH PROBLEM 2
April 11, 2016

Do you know WHEN and HOW to use the Row-Minus-Row Method? This method is used when the question involves several relationships between multiple items and for each relationship a Total is given.
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Question:
Kyle bought 6 similar pencils, 3 similar books and a file for $78.
1 pencil and 1 book cost $20.
1 pencil and 1 file cost $12.
What was the cost of the file?
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Solution using the Row-Minus-Row Method:
Given 6p + 3b + 1f = 78 ———–Row 1
Given 1p + 1b = 20
So 3p + 3b = 60 ———– Row 2
Row 1 – Row 2: 3p + 1f = 18 ———— Row 3
Given 1p + 1f = 12
So 3p + 3f = 36 ————- Row 4
Row 4 – Row 3: 2f = 18, so f = 9.
Ans: $9


