The blog postings are about the Singapore Math. The readers can learn from the postings on Solving Singapore Primary School Mathematics. You or your kids can learn dealing with Math modeling, Problem Sum from Lower Primary School to Upper Primary School level in Singapore school. This posting is a primary school math question on Ratio, Math Modeling and Problem sum.

You can read posting **Sarin and his coin bank** on the story of coin bank.

Read also posting on **Sarin and the million numbers** to understand concept of dollars and cents.

Read also the posting on **Sarin learns concept of ratio in school **to understand the concept of Ratio.

Upper primary school mathematics question UPQ184

Sarin and Hairu each have some twenty-cent coins in their coin bank in the ratio 4 : 7. Given that Hairu has $9 more than Sarin, how many twenty-cent coins does Sarin have?

Solution:

Draw the ratio model

The number of coins equivalent to $9.00 = 9 ÷ 0.2 = 45

Sarin had 7 – 4 = 3 units more 20-cent coins

3 units = 45

1 unit = 15

Sarin has 4 × 15 = 60 twenty-cent coins.

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