91
Adding and subtracting mixed numbers
Textbook: Part 3, lesson 91, pp. 63–65
GoalAdding and subtracting mixed numbers (when the fraction parts do not go past 1): whole parts and fraction parts are worked out separately.
New words
whole part · butun qismfraction part · kasr qismseparately · alohidasum · yig‘indi
Explanation
To add mixed numbers, add the whole parts and the fraction parts separately: 2 3/8 + 4 2/8 = (2 + 4) + (3/8 + 2/8) = 6 5/8. Subtraction is the same: 7 5/9 − 4 2/9 = (7 − 4) + (5/9 − 2/9) = 3 3/9. Adding a fraction to a whole number just puts the fraction next to it: 4 + 3/7 = 4 3/7.
Worked examples
3 2/9 + 4 5/9 = 7 + 7/9 = 7 7/9.
8 7/10 − 3 4/10 = 5 + 3/10 = 5 3/10.
Class activity
“Whole and fraction”: some cards have whole numbers, others fractions. Children choose pairs to make mixed numbers, then add and subtract them.
Practice
1
Work out 3 2/9 + 4 5/9.
7 7/9
2
Work out 8 7/10 − 3 4/10.
5 3/10
3
Work out 9 5/6 − 5/6.
9
4
One book has mass 2 3/10 kg and another 1 4/10 kg. What is the mass of both together?
3 7/10
5
A jug had 5 3/8 l of juice and 2 1/8 l was drunk. How much is left (l)?
3 2/8