89
Adding and subtracting fractions (practice)
Textbook: Part 3, lesson 89, pp. 57–59
GoalPractising adding and subtracting fractions: equations, ordering fractions, the difference of the largest and smallest.
New words
equation · tenglamadifference · ayirmaunknown · noma’lumcheck · tekshirish
Explanation
To order fractions with equal denominators, compare the numerators. To find the difference between the largest and smallest, subtract the numerators. Equations work like those with whole numbers: if x + a/n = b/n then x = b/n − a/n; if x − a/n = b/n then x = b/n + a/n. Check by substituting.
Worked examples
9/30, 14/30, 17/30, 21/30 is increasing order; the difference of largest and smallest is 21/30 − 9/30 = 12/30.
If x − 5/12 = 4/12 then x = 4/12 + 5/12 = 9/12. Check: 9/12 − 5/12 = 4/12.
Class activity
“Fraction chain”: the class forms a chain; each child adds their fraction to the previous result or subtracts it (same denominator). The last child says the result and everyone checks.
Practice
1
Write in increasing order: 14/30, 9/30, 21/30, 17/30.
9/30, 14/30, 17/30, 21/30
2
Find the difference between the largest and the smallest of those fractions.
12/30
3
Solve the equation: y − 5/12 = 4/12.
9/12
4
Work out 4/15 + 7/15 − 3/15.
8/15
5
Dilnoza drank 3/11 of the juice in a jug and Bobur drank 4/11. What part of the juice is left?
4/11