Fractions and the of operator
Concepts
- In fractions, the “of” operator is very commonly used and means “multiply.”
Theory
- Operators are things like “+” (add), “-” (subtract), “x” (multiply) and “/” (divide).
- They usually operate on things.
- For example in the expression 5 + 3
- “+” is the operator and the things it operates on are 5, and 3.
- In word problems using fractions a very common operator is the english word “of.”
- An example of this operator in use is: 1/2 of 12. Ans: 6.
- 1/2 of 12 = 1/2 x 12 = 6
Real World Usage
Open any cookbook and you will find the phrase “1/2 teaspoon of salt.” If a full tea spoon can hold 15 grams of salt, 1/2 of 15 gms is 7.5 grams. And that’s exactly what you need to add. Add more and you’ll have your guests spitting it out.
You go to the market to buy, say, dem apples, and notice the price is Rs. 200 per kg. You want 1/2 kg of apples. You’d have to pay 1/2 of 200, i.e. Rs 100.
Common Misconceptions
The main challenge learners will find is to:
- Not spot the “of” operator in the word question.
- Forget that “of” means multiply.
When teaching it is useful to highlight the “of” word in a different color, like so:
