Lesson 5 (Simultaneous Concept)

This will be the second last of out lesson. So, listen carefully to today lesson and remember there will be a test after Lesson 6 which is the last lesson. Topics taught today will be called the Simultaneous Concept. This concept when used in the right way, can assist us to solve non-rountine problems efficiently.

Question1 :

There are 45 pupils in a class. 60% of the boys and 20% of the girls wear spectacles. There are 19 pupils in the class who wear spectacles. How many girls wear spectacles?

Solution1 :
60% of the boys + 20% of the girls --> 19pupils

300% of the boys + 100% of the girls --> 95pupils

100% of the boys + 100% of the girls --> 45 pupils

200% of the boys --> 95 - 45= 50 pupils

20% of the boys --> 50 divide 10= 5 pupils

100% of the boys --> 5 x 5= 25 pupils

Number of girls in the class = 45 - 25
= 20

Number of girls who wear spectacles = 20% of 20
= 20/100 x 20
= 4#


Question2 :

5 apples and 3 oranges cost $2.70 altogether. 2 apples and 4 oranges cost $2.20 altogether. How much does a dozen apple cost?

Solution2 :

5 Apples + 3 Oranges --> $2.70

2Apples + 4 Oranges --> $2.20

20apples + 12 oranges --> $10.80

6 apples + 12 oranges --> $ 6.60

14 apples --> $4.20
12apples --> $3.60#


Question of the day:

There were 80 oranges and apples in a basketball at first. 2/5 of the oranges and 2/3 of the apples were eaten. In the end, there were 36 of these fruits left. How many oranges were there in the basketball at first?

Answer: 35#

This is the end of Lesson 5.

Reference from the book "Challenging Maths Problems Made Easy" by Ammiel Wan Chee Hong