I couldn’t resist summiting you this basic math problem on crazy Black Friday:
Offering an insane sale, a store is giving you an additional 50% rebate on an item already marked 40% down. What total discount percentage are you actually getting?
Some may promptly answer 90%...
…the correct result is 70%.
Original Price = 100%
First Rebate Price = Original Price – First Rebate x Original Price
First Rebate Price = 100 % - 40 % x 100% = 60%
Second Rebate Price = First Rebate Price – Additional Rebate x First Rebate Price
Second Rebate Price = 60% - 50% x 60% = 60% - 30% = 30%
Total Discount = Original Price - Second Rebate Price
Total Discount = 100% - 30% = 70% off
My quick mental calculation trick:
6 x 5 = 30% => Total Discount Price => 70% Discount
Mental calculation explanation:
Total Discount Price = (100%-40%) x (100%-50%) = 60% x 50%
Total Discount Price = (10 - 4) x (10 – 5) % = (6 x 5)% = 30% => 70% off
Some more examples:
30% rebate over a 30% rebate = 7 x 7 = 49% =>51% off
60% rebate over a 40% rebate = 4 x 6 = 24% =>76% off
10% rebate over a 20% rebate = 9 x 8 = 72% =>28% off
And so on…
One final example:
3 combined rebates of 10% 40% 50% = 9 x 6 x 5 = 9 x 3 = 27% =>73% off
I admit I cheated a bit on this last tricky one so the numbers would round up but the math still works.
Hope you can have fun juggling with amazing Black Friday discounts of your own!
That’s all from me today.
Happy holiday season to all!
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