Calculating percentages of percentages

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I am having a really hard time grasping how to effectively calculate "nested" percentages and the actual amount I save on each iteration

Example:

  • I purchase a gift card (Gift Card A) that has a \$200.00 value for a cost of $194.00 (3% discount)

  • Using Gift Card A value, I purchase Gift Card B that has a value of \$200.00 at the cost of $180.00 (10% discount)

  • Using Gift Card B value, I purchase Gift Card C that has a value of \$200.00 at a cost of $190.00 (5% discount)

  • Finally, using Gift Card C value, I purchase Gift Card D that has a value of \$100.00 at a cost of $90.00 (10% discount)

My first instinct would be that I saved a total of 28%, but I know it is not the case. If I use 0.97 * 0.9 * 0.95 * 0.9, I get 0.746415, which would be 25.36%. I am not sure if that is the correct answer and also do not know how I got there.

Also, I am unable to figure out how to calculate the actual amount I saved on each steps.

Thanks for any help!

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Well, how much money did you spend? 194 dollars.

How much purchasing power do you have: 20 on card A, 10 dollars on card B, 110 dollars on card C. And 100 dollars on card D. 240 total.

You have \$240 purchasing power for \$194. A saving of \$46 or 46/240 = 19 1/6% savings.