Home   >   Top of the Class   >   Son’s tricky formula to a math equation leaves dad scratching his head.

Son’s tricky formula to a math equation leaves dad scratching his head.

By on April 27, 2017

Dad: What is 40 divided by 5?
Son: Hmm.. 5+5= 10, right? Then 4+4= 8, right? So the answer is 8.
Dad: Wait, I’m not sure I follow you.

Robo Taro’s son might have gotten the right answer which is ‘8’ but  the mathematical expression heused to arrive at the answer was beyond dad’s mental abacus skills. After dad posted his dialogue with son on twitter, the tweet instantly went viral and was shared 7,000 times.  Curious twitter followers chimed in offering their own theories.  Parents with children attending Japanese school can learn a thing or two from this.

Twitter follower:  It could’ve been this.

Dad: Oh I see. My son’s in elementary grade just beginning to learn mathematical operations. I was thinking of :  80 divided by 5 as “80/5 = (100 – 20) / 5 = (50 + 50 – 20) / 5 = (20 – 4) = 16″  as a conventional math expression.  But then he might have used mental math.

Twitter follower: I think he got ‘8’ because…

40/5 = (40/5)*(2/2) = (40/(5*2))*2 ←5+5=10 = (40/10)*2 = 4*2 ←4+4=8 = 8

          Twitter follower:

This is a good example of using a different theory and hypothesis for math expressions. I am amazed by the flexibility of children.

Twitter follower: 

My take.  How many 5 yen coins do you need to have 40 yen?  40 yen is 4 10 yen coins. Since 2 5 yen coins make 10 yen, then 8 coins make 40 yen.

Twitter follower:

Twitter follower:  Perhaps my thought process is the same as your son’s.  I was influenced by educational toys when I was young; I’ve been calculating with 5 as a unit for around 40 years now.

 

About TF Tribe