70% Discount or 50% + 40%? Which One to Choose?

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Welcome back, my dear viewers. This time, we’re still going to discuss something not too far from the previous topic. If you’ve read my last article titled “Street Vendors”, then you’re somewhat on the right track. However, this time, I’ll talk about commerce in a more serious light—based on the concept of mathematics: discounts.

How do you feel when you hear that six-letter word? Heart pounding? (If yes, you might want to check your heart—there could be something wrong!) Getting goosebumps? Ladies, where you at?

Yes, the word discount is one of the favorite words for nearly everyone who loves to shop. Based on what we learn in formal education, discounts are introduced as early as elementary school and reinforced in 7th grade during the topic of social arithmetic. We learn formulas for calculating prices after discounts, and seasoned shoppers can calculate discounts very quickly. So, in this piece, I’m not going to teach you how to calculate discounts like you’re in elementary or middle school again. Instead, let’s dive into a more interesting and real-life case.

My first question: Discount—

Have you ever been to a supermarket? Or a mall? Have you seen a product labeled “Big Sale 70% Discount”? Or even more extreme, “Get a Discount Today Only: 50% + 40%”? (If you haven’t, feel free to go visit the nearest supermarket or mall. With a little luck, you might find the discount labels I just mentioned.)

Now, here’s the follow-up question: If you’re faced with two products of the same type, at the same original price, but placed in different booths—one labeled with a 70% discount, and the other with 50% + 40% discount—which one would you choose? Come on now, pick one! For your kids, your spouse, your best friend… or your best friend’s spouse—oops!

Starting to get confused? And then decide not to shop at all? I often pose this question to my colleagues and students. Most of them don’t answer right away—they have to think first. And after thinking for a moment and finally choosing, they often pick the wrong one. Clearly, if you apply the concept of discount calculation, you’ll confidently make the right choice.

It’s important to know that a 50% + 40% discount does not mean a 90% discount. So it’s a mistake if you think that way. The way merchants write “50% + 40% discount” is a strategy in the world of marketing—meant to trick your eyes and your mind. (As long as it’s not your heart that’s being tricked by the charming salesperson… just saying!)

Alright, let’s go back to the main issue.
Suppose the product in question is a shirt priced at Rp. 100,000.

Case 1: Apply a 70% discount.
70% of Rp. 100,000 is Rp. 70,000.
So the final price = Rp. 100,000 – Rp. 70,000 = Rp. 30,000.

Case 2: Apply a 50% + 40% discount.
Step 1: Apply 50% discount = Rp. 100,000 × 50% = Rp. 50,000
Step 2: Apply 40% discount to the remaining Rp. 50,000 → 40% of Rp. 50,000 = Rp. 20,000
So the final price = Rp. 50,000 – Rp. 20,000 = Rp. 30,000

So… huh? What? (Are those roosters crowing in the background?)
So what decision should you have made from the beginning?

The message I want to convey is this:

Especially to those who often ask, “What’s the point of learning this stuff? I don’t even use x and y when I shop at a stall.” Hmm… okay, fine. Here’s what I want to say: Stop complaining when learning something. Questioning the purpose of learning is the same as asking: What’s the purpose of life? Why are we born into this world?
The answer is simple: to become a better-quality human being.
And who wants to improve their quality? I’m sure the answer is: everyone.