29 Jan 2010
How mental math hurts children if they are not trained
Frank Ho, Amanda Ho
Ho Math and Chess Learning Centre
Room 1, 2265 West 41st, Vancouver, BC, Canada
BC certified Teacher
Vancouver, BC, Canada
Many math teachers will not let elementary students use calculators when they are in elementary schools, but not continue to use every opportunity to train students to continuously use the brain to calculate mentally has impede many students from getting A in math. The trouble is that may students contribute the reason of their calculation mistakes as “careless” without realizing the real reason is the lack of mental ability in calculating.
The following examples will demonstrate on how poor mental math ability will hurt a child’s chance of getting A in math.
1. Many children can do – 3 – (– 2), but when the expression is changed to vertical format without the apparent minus sign when doing long polynomial division then it causes problem for many students. For example, – 3 and – 2 are lined up vertically to get – 3 minus – 2, many students did wrong because the mental calculation without “seeing” the “–“ sign.
2. (x/2) –((x-1)/3) = 1/6
One teacher teaches students to remove the denominators by 3/3 time the first term and then 2/2 times the second term, it is alright but the training of mental calculation is non-existent so do multiply both sides by LCD of 6 to remove all denominators is much better for children to train their brain mentally.
3. Many times students are trained in a way that they simply lost sight on what to do; math is not done simply by only one direction and one track of mind.
It is not surprising to learn that student can do ½ + ¼ but can not do 1 ½ + 1 1/4 because he does not really understand the meaning between 1 and ½. It is also not surprising to learn that students cannot handle (1 – 4 ½)/ (3 + 1 ½) but the expression is changed to left and right format, many students recognize it and can do it.
The above examples demonstrated on how math is mentally presented to students in one way that they are able to handle but when the same or similar expression is presented to them in a different format then they get stuck and are not comfortable to handle them. The most important training is to get students to be familiar with different way of representing the same expression and also be able to handle them mentally.
Many times, students understand math in only one format but when the same question is changed to different representation then students get confused or get computation errors, and this is one reason that many student can not get A.
Frank Ho, Amanda Ho