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The whole point of the Khan Academy is to make money. To hell with whether it is any good or that there are content errors.
Comparing decimals. Decimal fractions (decimals for short — the numbers to the right of the decimal point) are a notoriously challenging topic in the elementary math curriculum. This difficulty is due at least in part to the fact that many rules that apply to whole numbers do not apply to decimals. Perhaps the most famous of these involves comparing numbers. When two whole numbers have different numbers of digits (e.g., 435 and 76), the one with more digits is greater (and usually by a lot!) This is not true of decimals: 0.435 is less than 0.76, despite having more digits.
Therefore, any attempt to help students improve their understanding of comparing decimals needs to deal with the case of decimals having different numbers of digits to the right of the decimal point. The standard American curricular treatment, in which students are instructed to append zeroes to the shorter decimal to equalize the number of digits helps students to perform this task correctly, but fosters its own misconceptions.
Khan Academy avoids this standard curricular approach. Instead, Khan has two videos involving comparing decimals. One is titled Comparing decimals; the other is titled, Decimals on a Number Line. In the first, Khan uses exactly one example, comparing 45.675 to 45.645. In the second, there is also exactly one example, comparing 11.5 to 11.7. In both cases, a student can get a correct answer by applying an incorrect rule (such as ignore the decimal point and treat what remains as a whole number). What is more, the accompanying explanation does nothing to address common misconceptions.
Khan is busted, but he will go on his merry way with his education con. After all, the masses don't need to even have much in the way of knowledge, just basic numeracy and literacy, for the lousy-paying jobs of tomorrow.
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