# Sarin participates in school anniversary event part 13 (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 will learn how to  deal with Math Modeling, Problem Sum from Lower Primary School to Upper Primary School level. This posting is an upper primary school math question on Fraction, Percentage and Problem Sum.

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

Read the posting on Sarin learns Average Number, Percentage and and Charting in school (Math Concept) to understand the concept of Percentage.

To read also the posting on Sarin learns the concept of Fraction (mathematics concept) to understand the concept of Fraction.

Upper primary school mathematics question UPQ240

Sarin’s teacher had given a box of pens to Sarin’s team for them to use during the school anniversary event.

There were some green and blue pens in a box.

If 5 green pens were removed from the box, the number of green pens left was 1/6 of the total number of the remaining pens.

If 9 blue pens were removed from the box, the number of green pens left was 25% of the total number of remaining pens.

How many pens were there in the box?

Solution:

1st scenario: 5 green pens removed and green pens remain was 1/6 of the remaining pens

2nd scenario: 9 blue pens removed and green pens remain was 25% of the remaining pens

Compare the 2nd scenario to the 1st scenario

A green or blue unit in 2nd scenario is a (green unit + 5) in 1st scenario

Redraw the two scenarios and the total pens are constant.

From the model

6 units + 5 = 4 units + 4 × 5 + 9

2 units = 20 + 9 – 5 = 24

1 unit = 12

The number of pens in the box = 6 × 12 + 5 = 77