a) 5.3 b) 4.99 c) 5.198 d) 5.04896
Children should have the ability to compare, order ad represent decimals (11, ACMNA105). The correct answer for the above question is 5.3. Some of the misconceptions could be:
some students may choose 4.99, with the misconception that 99 is the highest number, without considering the whole number, in which 4 is less than 5.
Students may rule out 4.99, compare the other three numbers, and choose 5.198, since 198 is bigger than 3.
Students may choose 5.0496 as this has five decimal places compared to other numbers which have less than four decimal places.
So, awareness about decimal place value is essential. Children need to recognise that the place value system can be extended beyond hundreds (11, ACMNA104).
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Sara has bought a rope to play. Dave attached another rope with a length of 3.86; after which the length was between 6.1 and 6.25 meters. What was the length of Sara's rope?
a) 2.62 b) 2.32 c) 3.67 d) 3.28
Option b) 2.32 is correct, since 3.86+ 2.32=6.18, which is between the specified range. Children should practice to add and subtract decimals, with and without digital technologies, and o check the reasonableness of answers, they should use estimation and rounding (11, ACMNA128).
Some of the misconceptions the children could make are:
Students may choose 3.28 (option d), simply by adding the decimal part of 3.86 and 3.26, where the resulting decimal point is between 1 and 25.
Some students may eliminate 3.67 and 3.28, as the whole number would become 7, and choose