# Sarin participates in school anniversary event part 11 (Math Question)

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The blog postings are about the Singapore Math. The readers can learn from the postings about 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 can learn deal with Math Modeling, Problem Sum from Lower Primary School to Upper Primary School level. This posting is a primary school math question on Ratio and Problem Sum.

Read the posting on Sarin participates in school anniversary event part 1 for story on school anniversary.

To read also the posting on understand the concept of Ratio.

Upper primary school mathematics question UPQ214

Sarin’s teacher went to a stationary shop to buy some pens for the school anniversary event. The stationary shop had some blue and red pens. There were twice as many red pens as blue pens. The shop sold the pens in bundles of 2 red pens and 3 blue pens. After selling all the blue pens to Sarin’s teacher, the shop still had 120 red pens left. How many pens did the stationary shop have at first?

Solution:

Ratio of the bundles, Red pens : Blue pens = 2 : 3

Since the ratio of red pens to blue pens = 2 : 1 = 6 : 3

The different number of red pens and blue pens or the red pens left is 6 – 2 = 4 units

Form the model

4U = 120

1U = 30

Number of red pens = 6 × 30 = 180

Number of blue pens = 180 ÷ 2 = 90

Total number of pens = 180 + 90 = 270