Tasty Math – Subtracting Sardines

15 Jul

Subtracting Sardines is the second title in Operatio’s Tasty Math Series.  As with Adding Apples, children are presented with a large calculator-like screen with a friendly character, in this case a penguin,  inviting them to choose a number.

Children select a number and see that number represented by blue sardines that tumble on to the screen.  They then select a number to subtract and watch as the number of subtracted sardines turn into skeletons. Children count the remaining sardines, each of which is frozen in a block of ice as they are tapped, while the skeletons disappear in a puff of smoke.  Sardines can be dragged, ice and all, around the screen.  Operatio has come up with a good way to show a difficult concept is a great way to show that something has been taken away, and it works well when the child has selected a number to subtract that is equal or lesser than the first number, but then things become……confusing.


Children can choose numbers larger than the first number to subtract, resulting in negative numbers.  4 – 9 would be illustrated like this:  4 blue sardines pop onto the screen.  4 then turn to skeletons, and then 5 red sardines appear.    At this point, my children are asking me why 4 – 9 = 5.  The answers to the left of the screen are displayed as negatives, but that is meaningless to my children.  When tapped, the fish turn into red skeletons, but that still doesn’t help them understand the “debt” that is part of the negative number concept.   If children are at the level where they need concrete representations of number (or, in this case, virtual representation), then they are not ready for the abstract concept of negative numbers.   My  7 y.0.  who can do all these calculations in his head now, was sharp enough to count the skeletons and match them to a negative number, but he still didn’t understand.  The whole concept is too confusing, but I can’t use the settings to turn it off.  I’d prefer s an option to grey-out numbers higher than the original number.  There could also be supportive feedback such as “You don’t have enough sardines to take 9 away.  Pick a smaller number.”  I have heard that a future update will have an option to turn off negative numbers.  I sincerely hope this is true.

This slideshow requires JavaScript.

All is not lost:  parent/teacher interactions can help overcome that confusion by providing the feedback not provided in the App.  You can prompt your child that there are not enough sardines to take away a larger number, and you can suggest smaller numbers.

Supportive Features

  • Operatio have picked a great way to show the basic concept of subtraction. The skeletons represent items that were there but have now gone.
  • The sardines roll, tumble and bump each other on the screen in  a very realistic way that is quite interesting to watch and play with, and it keeps the children “hooked”.  We’ve tried stacking the blocks of ice, but it is tricky.
  • Children can drag sardines around the screen as they count, although skeletons will disappear as soon as they are touched.
  • Freezing the sardines as each is counted can help with one-to-one correspondence.
  • As with the other apps in the series, three profiles are available, and this should be enough for most families.
  • Being able to restrict the numbers can be helpful for children who are just beginning to learn the concept.
  • The rewards are simple but motivating.


Even though there is one area that I’m not entirely happy with, Subtracting Sardines would be a handy homework aid for children in Prep and Year 1.   Children could use the App to model the problems on their homework sheets.  The characters are not “too cute” and would be age-appropriate for older children with special needs.   There is also the element of fun that makes the App interesting for children.  Parents and Teachers can overcome the confusing negative numbers issue with appropriate feedback.  It is great value for the price.
Publisher:  Operatio
Price: 99 cents
iPad Version

Subtracting Sardines HD - Operatio

iPhone Version

Subtracting Sardines - Operatio


One Response to “Tasty Math – Subtracting Sardines”


  1. Tasty Math – Multiplying Acorns « On Sarah's iPad - 30/07/2012

    […] app in Operatio’s Tasty Math App series, the others in the series being Adding Apples and Subtracting Sardines.  It is aimed at young children learning the concept of multiplication, but the characters would […]

Comments are closed.

%d bloggers like this: