Subtracting mixed numbers and calculating with fractions
Subtract mixed numbers, open up a whole when needed, solve expressions with complex fractions and scale up a recipe.
- إيران: الصف ٥
- ألمانيا: الصف ٦
لم يُترجَم هذا المختبر إلى هذه اللغة بعد.
الدليل
To subtract كسر مركبs you can subtract the whole numbers first and then the fractions. If the fraction of the first number is smaller than the second, open up a whole and turn it into a fraction: ٣١٥ = ٢٦٥. Then subtract.
Another way is to turn both into improper fractions: ٥١٤ = ٢١٤. Then subtract the numerators, keep the denominator, and turn the answer back into a mixed number.
A common mistake is to subtract "small from big" in the fractions: in ٢١٥ − ٣٥, you must not do ٣٥ − ١٥. Open up a whole first.
In an expression with several operations, work out the top of the fraction first, then divide. Dividing by a fraction means multiplying by its reciprocal. A fraction whose numerator or denominator is a fraction is a كسر بسطه ومقامه كسران.
To scale up a recipe, first work out the amount for one person or one glass, then multiply by the number.