Solving these word problems
This chapter's word problems use three skills: coordinates, ratio and proportion. First read the question and spot which skill you need, because they are solved in different ways. Then work through it carefully using the 4-step plan below so you do not miss anything.
Key idea / 4 steps
1) Understand — what is asked? 2) Plan — ratio, proportion or coordinates? 3) Solve — find one unit, or add ratio parts, or count grid units. 4) Check.
Which skill?
Sharing in a fixed comparison → ratio. Price or amount that scales up → proportion (find the value of one, then multiply). Position or distance on a grid → coordinates.
Worked example
A shop sells 3 books for RM15. How much do 5 books cost?
This is proportion. Cost of 1 book = RM15 ÷ 3 = RM5.
Cost of 5 books = 5 × RM5 = RM25.
Remember
- Proportion: find one, then multiply.
- Ratio sharing: add the parts, divide the total.
- Grid distance: subtract the coordinates on the same line.