NB Francophone G6 Math common mistakes
NB Francophone G6 Math · Understand the traps and how to avoid them.
In 12,5 + 3,75, lines up the final digit of each number instead of the decimal commas, so tenths and hundredths are added in the wrong columns.
The learner treats decimal numerals as whole-number strings and right-aligns them, ignoring that the decimal comma fixes place value.
What to do instead
Rewrite 12,5 as 12,50, place both numbers in a place-value chart with a comma column, estimate the sum (about 16), add column by column, then compare with the estimate.
Writes 3/8 = 0,38 or 3/8 = 38% by copying the numerator and denominator into decimal or percent form.
The learner memorises fraction-to-decimal conversion as a digit-copying rule rather than as division or a part-whole comparison.
What to do instead
Use a one-unit strip divided into 8 equal parts and shade 3; connect 3 ÷ 8 = 0,375 and ×100 = 37,5%; compare with benchmarks 1/2 = 0,5 and 1/4 = 0,25.
Evaluates 20 − 4 × 3 as 48 by working left to right: 20 − 4 = 16, then 16 × 3 = 48.
Reading direction dominates, and multiplication's precedence is not attached to a meaning the learner can check.
What to do instead
Bracket the multiplication first as 20 − (4 × 3); model it as removing 4 groups of 3 from 20; then practise mixed expressions with and without brackets, naming the operation order aloud.
If 3 pens cost 6 $, says 5 pens cost 8 $ by adding 2 pens and 2 $.
Additive reasoning: the learner treats both quantities as increasing by the same absolute amount rather than by the same factor.
What to do instead
Build a ratio table to find the unit rate (2 $ per pen), then multiply 5 × 2; compare the result with the additive guess and explain why doubling the quantity doubles the cost.
For 3, 6, 12, 24, predicts 27 because the first jump is +3, ignoring that later jumps are +6 and +12.
The learner generalises from the first pair only and does not test the rule against all terms.
What to do instead
Make a two-row table of terms and successive differences; when differences are not constant, check ratios (×2) and test the rule on the fourth term before predicting.
For x + 7 = 15, subtracts 7 only from the left side and writes x = 15.
The equals sign is read as 'gives the answer' rather than as a balance between two equal quantities.
What to do instead
Use a balance model: subtract 7 from both sides, record x + 7 − 7 = 15 − 7, then substitute x = 8 into the original equation to verify both sides equal 15.
For a 6 cm by 4 cm rectangle, gives the area as 20 cm (the perimeter) or the perimeter as 24 cm² (the area).
Formulas are recalled as strings without the boundary-versus-covering distinction, and units are not used as a check.
What to do instead
Trace the border with a string for perimeter in cm and cover the rectangle with cm² tiles for area; label each result with its unit and compare fence versus paint contexts.
Calculates the volume of a 2 m by 30 cm by 50 cm box as 2 × 30 × 50 = 3 000 cm³ without converting 2 m.
The learner treats all given numbers as the same unit and does not check unit compatibility before multiplying.
What to do instead
Convert 2 m to 200 cm first, estimate 200 × 30 × 50 = 300 000 cm³, multiply, then express the result in m³ (0,3 m³) and check reasonableness.
On a bar graph whose axis marks every 5 units, reads a bar reaching the third mark as 3 instead of 15.
The learner counts gridlines as single units and ignores the axis labels and interval size.
What to do instead
Write the value of each axis mark before reading any bar; calculate one interval (5), count intervals rather than lines, and verify against a table of the graph's data.
Says rolling a 6 is impossible because 6 is only one of six outcomes, or calls a 50% chance certain.
Everyday chance words are used without linking them to the number of favourable outcomes over total outcomes.
What to do instead
List the sample space 1 to 6, count favourable outcomes, write probability as a fraction and percent, and place events on a 0-to-1 probability line labelled impossible, unlikely, even chance, likely and certain.