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Computing Savings

Computing Savings

“Blinko Supermarket sells 8 kg of flour for $5.76. Bankit Store sells 12 kg of flour for $6.48. How much will I save when buying 20 kg of flour at Bankit Store by comparison with buying the same amount at Blinko Supermarket?

  1. $3.60
  2. $2.80
  3. $2.40
  4. $2.20
  5. $1.80”

This question given in the upper primary group of the 3rd International Vedic Mathematics Olympiad (IVMO 2023) held last November 2023 can be easily solved using the traditional method. However, many contestants failed to submit the correct answer due to the time pressure.

The usual solution to this type of problem is to get the price per kilogram in the two stores, get the difference and multiply the difference by twenty to get the savings.

$5.76/8 kg = $ 0.72/kg at Blinko Supermarket

$6.48/12 kg = $ 0.54/kg at Bankit Store

Note that many 11 years-old and younger kids may find difficulty in dividing by 8 and 12 without using pen and paper.

$ 0.72 – $ 0.54 = $ 0.18/ kg – the difference in their prices

$ 0.18/kg x 20 kg = $ 3.60/20 kg, which is choice A.

Since the prices are given for 8 and 12 kilograms, we can use an easier solution by getting the greatest common factor of 8 and 12  which is four kilograms.

($5.76/8 kg)/2  = $ 2.88/4 kg at Blinko Supermarket

($6.48/12 kg)/3 = $ 2.16/kg at Bankit Store

Dividing by 2 and 3 is much easier than dividing by 8 and 12.

$2.88 – $ 2.16 = $ 0.72/4 kg – the difference in prices of the two stores

$ 0.72/4kg x 5 = $ 3.60/20 kg.

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