Sarin and his coin bank part 16(Math Question)

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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.

Lower primary school mathematics question LPQ48

Sarin had a total of twenty $10-notes and $5-notes in his coin bank. The total value of all the notes was $120. How many $10-notes did he have?

Solution:

            A set of 1 $10-note and 1 $5-note give value of = 10 + 5 = $15

            If there are 10 sets, the value = 10 × 15 = $150

            It is more than $120 by $30

            To reduce $10-notes and increase $5

            We needs to reduce 30 ÷ 5 = 6 $10-notes to get to $120

            The number of $10-notes = 10 – 6 = 4

            The number of $5-notes = 10 + 6 = 16

Alternative solution:

            Use guess and check method

            Start the guess from 10 $10-notes and 10 $5-notes

            Remember the total number of notes = 20 (1st check)

            Then base on total value coputed to decide increase or reduce the number of notes

             Sarin has 4 ten dollar notes in his coin bank.

More problem sum questions click here

More guess and check questions click here

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