# Hairu shares his stickers part 32 (Math Question)

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The blog postings are about the Singapore Math. The readers can learn from the postings on Solving Singapore Primary School Mathematics. The blog presenting the Math Concept, Math Questions with solutions that teaches in Singapore Primary Schools. You or the kids will learn the skills of dealing with Math Question Solving, Math Modeling and Problem Sums from Lower Primary School to Upper Primary School level after reading the blog postings. This posting is an upper primary school math question on Ratio, Math ModelingAverage Number and Problem Sum.

You should also read the posting on Sarin learns Average Number, Percentage and Charting in school (Math Concept) to understand about Average Number.

You can read the postings on Sarin learns concept of ratio in school to understand the concept of Ratio.

Challenge yourself with the question before look out for the given solution‼!

Upper primary school mathematics question UPQ284

Hairu had twice as many stickers as Sarin at first. After Hairu bought another 20 stickers and Sarin bought another 105 stickers, Sarin had three times as many stickers as Hairu.

(a) How many stickers did Sarin have at first?

(b) Find the average number of stickers the two of them had in the end.

Solution:

Based on at the end Sarin has 3 times stickers as Hairu

By fitting in also the number of stickers each of them bought and draws the model

Per the model

You can see the green block is equal to 2 purple blocks plus 20

Sarin had 3 times of Hairu at the end

So Sarin had 3 time the purple blocks plus 20 that Hairu had

5 units = 105 – 20 – 20 – 20 = 45

1 unit = 9

Sarin had 9 stickers at first

Total number of stickers together in the end = 3 × 9 + 105 + 20 = 152

The average number of stickers the two of them had at the end = 152 ÷ 2 = 76

Alternative solution:

Stickers ratio before, Hairu : Sarin = 2 : 1

Hairu bought 20 stickers and Sarin bought 105 stickers

Stickers ratio after, Hairu : Sarin = 1 : 3 = (2U + 20) : (1U + 105)

6U + 60 = 1U + 105

5U = 45

1U = 9

Lisa had 9 stickers at first

Total number of stickers at the end = 3U + 125 = 27 + 125 = 152

The average number of stickers the two girls had at the end = 152 ÷ 2 = 76