The cost of one ruler is $0.70
Applications of simultaneous equations
From the question, we are to determine the cost of one ruler
Let x represent the cost of a ruler
and
y represent the cost of a pen
From the given information, we can write that
y + x = $2.10 ----------- (1)
2y + 3x = $4.90 ----- (2)
From equation (1),
y + x = $2.10
Then,
y = $2.10 - x
Substitute this into equation (2)
2y + 3x = $4.90
2($2.10 - x) + 3x = $4.90
$4.20 - 2x + 3x = $4.90
$4.20 +x = $4.90
x = $4.90 - $4.20
x = $0.70
Hence, the cost of one ruler is $0.70
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