# Sarin and his coin bank part 34 (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 the skills of dealing with Math Modeling, Problem Sum from Lower Primary School to Upper Primary School level after reading the blog postings. This posting is an upper primary school math question on Percentage, Ratio and Problem Solving.

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

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

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

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

Upper primary school mathematics question UPQ338

Sarin has 200 coins in the coin bank. 55% of them are 20-cent coins and the rest are 50-cent coins. He decided to deposit 30% of the 50-cent coins into a bank. How much did he deposit?

Solution:

The total number of 50-cent coins = 200 × 45% = 90

The number of 50-cent coins deposit to bank = 90 × 30% = 27

The amount that deposit to bank = 27 × 0.5 = \$13.50

Alternative Solution:

Ratio of number of 50-cent coins to 20-cen coins = 55 : 45 = 11 : 9

Draw the math model

From the model

20units = 200

1 unit = 10

The number of 50-cent coins = 9 × 10 = 90

Ratio of number of 50-cent coins to 50-cent coins deposit to the bank = 70 : 30 = 7 : 3

Draw the math model

From the model

10 units = 90

1 unit = 9

The number of 50-cent coins deposit to bank = 3 × 9 = 27

The amount that deposit to bank = 27 × 0.5 = \$13.50