In a Singapore canteen, a plate of chicken rice costs $a and a fruit juice costs $b. The total cost of 3 plates of chicken rice and 4 fruit juices is $20. Stan orders 6 plates of chicken rice and 8 fruit juices for his friends and pays with a $50 note. How much change should Stan get back?
Show Worked Solution
Worked Solution
Step 1: Notice that 6a + 8b = 2 × (3a + 4b) — Stan's order is exactly DOUBLE the original order.
Step 2: Cost of the original order: 3a + 4b = $20.
Step 3: Cost of Stan's order: 2 × $20 = $40.
Step 4: Change = $50 − $40 = $10.
Answer: $10
Correct answer: $10
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