Tag Archives: speed math

Dried Fish Arithmetic in Action

by Ike Prudente

Once when I was with my brother Rene’s Balikbayan family in the dried fish market in Taboan, Carbon, Cebu City, we bought some “danggit” and “pusit”

  • Ike:  
    Magkano ang pusit?
  • Vendor:
    P680 po.
  • Ike:
    Pabili ng isang kilo. Wala na bang tawad?
  • Vendor:
    Pwede po P640. Mura na po iyan…
  • Blessie(my sister-in-law):  
    Sige, pabili na rin ng kalahati.

After the vendor had vacuum-packaged the pusit, we asked her the price of dried Danggit .

  • Ike:  
    Magkano ang danggit?
  • Vendor:
    Bigyan ko na po kayo ng discount. P 180 po.
  • Ike:
    Pabili ng dalawang kilo para sa akin, at isang kilo para sa hipag ko.
    (then instantly added)
    Heto ang P 1,000.  Keep the change!
    Heto ang P 500 mula sa hipag ko. Keep the change!
    Pag kulang, bibigyan pa kita ng dagdag na P 500, keep the change!
  • Vendor:  
    Naku, maraming,  Maraming, MARAMING SALAMAT PO!

With a sweet smile, she grabbed her calculator, and excitedly punched the numbers, even before she packed the danggit, wanting to know how much is the “change” she will keep,

But her smile quickly vanished, and she exclaimed

  • Vendor:
    Ang galing mo naman Sir!

Do you know why?

Most people (like our vendor) would calculate the pusit first.

  • P 640 per kilo x 1 kilo = P 640.
  • P 640 per kilo x half kilo = P 320

Then calculate the danggit:

  • P180 per kilo x 2 kilos = P360
  • P 180 per kilo x 1 kilo = P 180

So after this lengthy computation, she adds them all up to compute the grand total :
P640 + P 320 + P360 + P180 = P1,500!

Walang sukli!

I did a much simpler computation in my head.

  • I purchased one kilo of pusit at P 640 per kilo, plus two kilos of danggit at P180 per kilo.
    P 640 + 2 * P 180 = P 1,000. I paid the vendor P1,000, so there is no change from me!
  • My sister bought exactly half of what I bought,
    P 1,000 / 2 =  P 500,   She paid the vendor P 500, so there is no change from my sister-in-law too!

Mental Math/Speed arithmetic is always useful, even when buying dried fish in a “palengke” in Cebu!

I remember we all had a good laugh that day! So I did give Manang a little extra. Remember she gave us a P 40 per kilo discount on the dried pusit? And we bought 1.5 kilos? I decided to give her back half the discount.  You do the math.

Dried Fish Stall

Mental Math is always useful, even when haggling with dried fish vendors!


And in case you have not yet figured it out:

  • P 680 – P640 = P40
  • P40 * 1. 5 = P60
  • Half of P 60 is P30.

We had fun that day, so I  gave her P30

  • Ike:
    Hati na lang tayo sa discount.  Bigyan kita ng P30.  Maraming salamat Manang!
  • Vendor:
    Maraming salamat din po!


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