White chocolate costs Php 20.00 per bar, and dark chocolate costs Php 25.00 per bar. If Janine bought 15 bars of chocolate for Php 340, how many bars of dark chocolate did she buy?
Step 1. Let x ____________
Let y ____________
Step 2: Equation 1:
Equation 2:
Step 3: Solution
Step 4: Check
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Step 1
Let x be the no. of white chocolates
Let y be the no. of dark chocolates
Step 2:
Equation 1: x + y = 15
Equation 2: 20x + 25y = 340
Step 3:
Divide 5 to both sides to make it easier to solve
4x + 5y = 68
Eliminate x by subtracting 4x + 5y = 68 4 times to the 1st equation
4x + 5y - 4(x+y) = 68 - 4(15)
4x + 5y - 4x - 4y = 8
y = 8
Since 20x + 25y = 340 and y = 8, then we can solve x
20x + 25(8) = 340
20x + 200 = 340
20x = 340 - 200 = 140
x = 140/20 = 7
Step 4:
x + y = 15
7 + 8 = 15, which satisfies the 1st equation
20x + 25y = 340
20(7) + 25(8) = 340
140 + 200 = 340, which satisfies the 2nd equation
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