P6 Math: Blue and Red Crayons

At first, 70% of the crayons in a box were blue and the rest were red. After Tze Jun placed another 36 blue crayons and 42 red crayons into the box, the ratio of the number of blue crayons to the number of red crayons became 5:3. How many crayons were there in the box in the end ?

Solution:

                   

See the model and chart

At the end:

6u = 102 --> u = 17

At first: 7u = 119 blue crayons and 3u = 51 red crayons.

At the end, there are:

• 119 + 36 = 155 blue crayons
•  51 + 42 = 93 red crayons
• Total = 155 + 93 = 248 crayons