Percentage - Lesson 3
Calculating the percentage of a number.
Calculating the following percentage can be difficult for learners.
In the example above 34 is 85% of what number??
- Learners will see that the example given can be put as an equation.
- Take the sentence and break it down.
- "34 is", can be written as 34 =
- "85 % of a number" can be written as 85% of x ( use any letter as the unknown number)
- Now that the number sentence is done, we can write it as an equation.
34 = 85% of x
- Step 1: Place the 85 over 100 ( Percentage is always over 100)
- Step 2: Change the of to a times (x)
- Step 3: Put the unknown (x in this case) over 1, to also make it a fraction.
- Step 4: Doing equations, we know that if we do something on the right hand side, we also have to do it on the left hand side.
- Step 5: We want to get the x (the unknown number alone). To do that we have to get "rid" of the fraction.
- To do so we can multiply with the reciprocal. (Reciprocal means that we multiply with the opposite of the fraction) If the fraction is 85 over 100, we multiply with 100 over 85.
- This will give us the x alone on the right hand side.
- We also have to multiply with 100 over 85 on the left hand side.
- Again, if learners can simplify, the can do the simplifying method. If they can't, they can multiply the fraction at the top and at the bottom.
- The answer they get will be 3400 over 85. Divide this fraction.
- The final answer will be 40.
Learners can now see that 34 is 85% of the number 40.
Below are a few exercises learners can practice:
Learners can follow the same steps that were used in the example.
Do a few sums with your learners and then give them some on their own too. Make sure that all your learners understand this work.
