Sarin participates in school anniversary event part 8 (math question)

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

Read 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 UPQ136

Teacher in charge of the event prepared a box of pens and pencils to use in the school anniversary event. If the teacher took out 140 pencils, 1/3 of the remaining items in the box were pencils. If the teacher took out 25% of the pens, then ¼ of the remaining items in the box were pens.

(a) How many pens were there in the box at first?

(b) How many pencils were there?

Solution:

                         Draw the math model based on the above two ‘if’s.

                         To note that the number of pens and pencils are constant

                         25% of the pens ==> 1/4 of the total number of pens

                           From the model,

                                  7 units = 140

                                  1 unit = 20

                           Pens in the box at first = 4 × 20 = 80

                           Pencils in the box = 9 × 20 = 180

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