92
Adding mixed numbers
Textbook: Part 3, lesson 92, pp. 66–68
GoalAdding mixed numbers when the fraction parts add to an improper fraction: take out the whole and add it to the whole parts.
New words
carrying over to a whole · birlikdan o‘tishtaking out the whole · butun qismni ajratishfraction part · kasr qismsum · yig‘indi
Explanation
If the fraction parts add up to an improper fraction, take the whole out and add it to the sum of the whole parts. For example 3 5/7 + 1 4/7 = (3 + 1) + (5/7 + 4/7) = 4 + 9/7 = 4 + 1 2/7 = 5 2/7. The same happens when two proper fractions give an improper one: 5/9 + 7/9 = 12/9 = 1 3/9.
Worked examples
4 7/8 + 1 3/8 = 5 + 10/8 = 5 + 1 2/8 = 6 2/8.
1 4/6 + 2 3/6 = 3 + 7/6 = 3 + 1 1/6 = 4 1/6.
Class activity
“Complete the whole”: pupils cut paper circles into quarters and eighths and show that when fraction parts are added they can complete a whole circle.
Practice
1
Work out 2 4/9 + 3 8/9.
6 3/9
2
Work out 4 7/8 + 1 3/8.
6 2/8
3
Work out 5/9 + 7/9 and write it as a mixed number.
1 3/9
4
A rectangular flower bed is 3 7/10 m long and 2 6/10 m wide. What is its perimeter in metres? (Add the four sides.)
12 6/10
5
Nodira spent 1 4/6 hours drawing and 2 3/6 hours on a project. How many hours did she work in total?
4 1/6