Mathematics for IGCSE & O level - Ratio And Proportion (Section 6 - No. 31)
If the price of 4 pens is $7, which is/are correct?
The cost of 8 pens is $14.
The cost of 1 pen is $1.75.
The cost of 12 pens is $28.
The cost of 2 pens is $3.50.
คำอธิบาย
Cost/pen = 7/4 = $1.75. 8 pens = 8 * 1.75 = 14. 2 pens = 2 * 1.75 = 3.50.